backside

(as) bald as a baby's backside

slang Totally bald. My father had long hair as a teen, but now he's bald as a baby's backside.
See also: backside, bald

(as) soft as a baby's backside

Exceptionally soft and smooth. I love how your face feels after you shave—it's as soft as a baby's backside! This is my favorite blanket to get snuggled up in at night. It's soft as a baby's backside, and it keeps me nice and warm in bed.
See also: backside, soft

a kick up the backside

A forceful gesture or message of some kind (usually delivered with good intentions) that acts as motivation to the (previously unmotivated) recipient. Primarily heard in UK, Australia. The threat of divorce was the kick up the backside he needed to start working on improving his marriage.
See also: backside, kick, up

as if the sun shines out (one's) backside

As though someone or oneself is better or more important than others. Various slang and vulgar synonyms for "backside" are often substituted. (Note: If one thinks this about oneself, it means that one is arrogant, conceited, or self-absorbed. If someone thinks this of another person, it means that they love or admire that person to such a degree as to be blinded to any of their potential faults.) Samantha has such an ego and acts as if the sun shines out her backside. She's absolutely head-over-heels in love with Martin. Even though I find him a bit irritating, to her it's as if the sun shines out his butt.
See also: backside, if, out, shine, sun

bald as a coot

Totally bald. My father had long hair as a teen, but now he's bald as a coot.
See also: bald, coot

get off (one's) backside

slang To start being productive, especially after one has been inactive (and perhaps literally sitting). This phrase is often used as an imperative. Get off your backside and help me with this! If you don't get off your backside now, you'll be up all night finishing your paper.
See also: backside, get, off

think the sun shines out (of) (one's) arse

rude slang To believe a person is better or more important than others or above reproach. (Note: If thought about oneself, it means that one is arrogant, conceited, or self-absorbed. If someone thinks this of another person, it means that someone loves or admires that person to such a degree as to be blind to any of their potential faults.) Primarily heard in UK. Tom has acted like he's such a hotshot after getting the promotion. He thinks the sun shines out his arse! He's absolutely head-over-heels in love with Mary. Even though I find her a bit irritating, he thinks the sun shines out her arse.
See also: arse, out, shine, sun, think

think the sun shines out (someone's) backside

To believe a person is better or more important than others or above reproach. (Note: If thought about oneself, it means that they are arrogant, conceited, or self-absorbed. If someone thinks this of another person, it means that they love or admire that person to such a degree as to be blind to any of their potential faults.) Tom has acted like he's such a hotshot after getting the promotion. He thinks the sun shines out his backside! He's absolutely head-over-heels in love with Mary. Even though I find her a bit irritating, he thinks the sun shines out her backside.
See also: backside, out, shine, sun, think

work (one's) backside off

To work really hard (on or at something). I know you thought it was just a silly New Year's resolution, but I've been working my backside off at the gym! Sally and Jim work their backsides off when we hold our consumer conference each year. I don't know what I'd do without them!
See also: backside, off, work
Farlex Dictionary of Idioms.

*bald as a coot

 and *bald as a baby's backside
completely bald. (*Also: as ~.) If Tom's hair keeps receding like that, he'll be bald as a coot by the time he's thirty. Fred: Now, I'll admit my hair is thinning a little on the top, butJane: Thinning? You're not thinning, you're as bald as a baby's backside!
See also: bald, coot

*soft as a baby's bottom

 and soft as a baby's backside; *soft as down; *soft as silk; *soft as velvet
Cliché very soft and smooth to the touch. (*Also: as ~.) This cloth is as soft as a baby's bottom. The kitten's fur was as soft as down. Your touch is soft as silk. This lotion will make your skin soft as velvet.
See also: bottom, soft
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

a kick up the backside

BRITISH, INFORMAL, RUDE or

a kick in the butt

AMERICAN, INFORMAL, RUDE
COMMON If someone or something gives someone a kick up the backside, they shock them into trying harder to do something. I hope this gives him the kick up the backside he needs. Maybe he'll try harder to look for a job now. Note: This expression is often varied. For example, in British English up the arse or in the pants can be used instead of up the backside, and in American English in the ass can be used instead of in the butt. He got four goals. But he needed a kick up the arse before he started to play properly. Note: You can also say that a person or event kicks someone up the backside or in the pants. Did you think universities needed kicking up the backside a little bit? He sometimes had to be kicked in the pants to make full use of his athletic gifts.
See also: backside, kick, up
Collins COBUILD Idioms Dictionary, 3rd ed.

(as) bald as a ˈcoot

having no hair on your head at all: Why did you buy him a hairbrush? He’s as bald as a coot!
A coot is a black bird with a white patch on its forehead that lives on or near water.
See also: bald, coot

a kick up the ˈbackside

(also a kick in the ˈpants) (informal) a shock, strong criticism, etc. which encourages somebody to do something or to behave better: What he needs is a good kick up the backside. Then he’d do some work.
Your backside is the part of the body that you sit on.
See also: backside, kick, up

think the sun shines out of somebody’s ˈarsetaboo/backˈside

(British English) (American English think the sun shines out of somebody’s ˈass taboo) (slang) have a very high opinion of somebody and think that everything they do is good: We need more money for this job. I think you should be the one to ask the boss — he thinks the sun shines out of your backside!
See also: arse, backside, of, out, shine, sun, think
Farlex Partner Idioms Dictionary

backside

n. the buttocks; one’s rear. There is some mustard or something on your backside.
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (as) bald as a baby's backside
  • bald
  • coot
  • as bald as a coot
  • be as bald as a coot
  • bald as a coot
  • (as) soft as a baby's backside
  • bald as a coot/billiard ball
  • (as) soft as a baby's bottom
  • soft as a baby's bottom
References in periodicals archive
* GAS: (Guard After Snapper) is a fold block between the backside guard and the center blocking the 1st level defender and the backside guard working to the 2nd level defender.
Similarly, thongs are a pain in the backside, literally.
The key to effective use of a screw vent is to turn the screw from the backside of the die each time the die coating is sprayed over the pin.
Glass beads have many advantages: they provide a rigid, hermetic connection point and the fragile backside connection is not disturbed by movement or removal of the connector.
Dubai: An engineer has been accused of molesting his co-worker by slapping on her backside at their workplace, heard a court on Monday.
Crooked grind to backside lipslide and/or frontside boardslide body varial to lipslide.
The photographer, from Waterford, told the Irish Mirror: "I got a backside straight into the face, but the camera kept rolling and captured the reaction to it."
Froome, cleared of using an illegal skin suit by Tour chiefs, suffered gravel rash on his backside but otherwise escaped unhurt without losing any time to rivals.
Read: (http://au.ibtimes.com/articles/572618/20141113/backside-battle-next-display-arena-bosom-war.htm) After Backside Battle, Next Display Arena Is The Bosom War as Female Celebrities Le By Kim Kardashian Bare Frontal Assets
London, July 23 ( ANI ): England cricket team coach Peter Moores has given his senior players a verbal 'kick' up their 'backside' and told them that it is time to deliver.
ALEX GREGORY admitted Britain men's four received a "kick up the backside" yesterday with their semi-final defeat to arch rivals Australia at the Munich World Cup.
Q MY twoyear-old rabbit is having trouble with her stools sticking together on her backside. It gets so bad that we have to soak it off!
Johnson had grown so bemused by his defender's lack of a goal for him, both at Yeovil and at City, that he promised to bare his backside in Burton's window should he ever find the net.
In the Inside Zone Read Option, the offensive line and then running back run the inside zone play and the QB reads the backside DE.