kick in the (seat of the) pants, a

a kick in the pants

1. A forceful gesture or message of some kind (usually delivered with good intentions) that acts as motivation to the (previously unmotivated) recipient. These days, teenagers seem to need a swift kick in the pants to convince them to do well in school. That speeding ticket was the kick in the pants that Dan needed to get his driving under control.
2. A frustrating or unwelcome occurrence. Having to move back in with my parents at age 40 is a real kick in the pants.
3. A source of pleasure or enjoyment. Our night out was a real a kick in the pants—we had a great time.
See also: kick, pant
Farlex Dictionary of Idioms.

kick in the (seat of the) pants

 and kick in the ass; a kick in the butt; a kick in the teeth
Fig. Inf. a strong message of encouragement or demand. (Use ass and butt with discretion.) All he needs is a kick in the seat of the pants to get him going. A kick in the butt will get her moving.
See also: kick, pant
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

a kick in the pants

INFORMAL
A kick in the pants is a something that forces someone to act more quickly and effectively or which punishes them if they do not. Some of us in the business community need a kick in the pants. It's a kick in the pants for the politicians who promise to deliver and then fail to do so.
See also: kick, pant
Collins COBUILD Idioms Dictionary, 3rd ed.

a kick in the pants (or up the arse or backside)

something that prompts or forces fresh effort. informal
1996 Southern Cross On Saturday night, Mr Groom said the party understood the electorate had given the Liberals a kick in the pants.
See also: kick, pant
Farlex Partner Idioms Dictionary

kick in the pants

verb
See kick in the seat of the pants
See also: kick, pant
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions

kick in the (seat of the) pants, a

A reproof or reprimand; also, a goad or spur to get someone moving. Both can be literal or figurative. The idea must be very old indeed, and the expression, a euphemism for a kick in the posterior, appeared in Samuel Butler’s Hudibras (1663). A more recent term with the same meaning as the first sense is a kick in the teeth, used from the mid-twentieth century on.
See also: kick, of
The Dictionary of Clichés by Christine Ammer
See also:
  • a kick in the pants
  • kick in the pants
  • kick in the pants, a
  • a kick in the butt
  • kick in the butt
  • a kick up the backside
  • an iron hand
  • iron hand
  • kick in the rear