thick as thieves

(as) thick as thieves

Having a close, intimate friendship or alliance. Anna and Beth are together all the time these days—they're as thick as thieves. The guys who work in the warehouse are thick as thieves. They don't really socialize with anyone else in the company.
See also: thick, thief
Farlex Dictionary of Idioms.

*thick as thieves

Cliché very close-knit; friendly; allied. (Thick = close and loyal. *Also: as ~.) Mary, Tom, and Sally are as thick as thieves. They go everywhere together. Those two families are thick as thieves.
See also: thick, thief
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

thick as thieves

Intimate, closely allied, as in The sisters-in-law are thick as thieves. This term uses thick in the sense of "intimate," a usage that is obsolete except in this simile. [Early 1800s]
See also: thick, thief
The American Heritage® Dictionary of Idioms by Christine Ammer.

thick as thieves

If two or more people are as thick as thieves, they are very friendly with each other. Jones and Cook had met at the age of ten and were as thick as thieves. Grant went to school with Maloney, the other lawyer in town. They're thick as thieves.
See also: thick, thief
Collins COBUILD Idioms Dictionary, 3rd ed.

thick as thieves

(of two or more people) very close or friendly; sharing secrets. informal
See also: thick, thief
Farlex Partner Idioms Dictionary

(as) thick as ˈthieves (with somebody)

(informal) (of two or more people) very friendly with each other, especially in a way that makes other people suspicious: Those two are as thick as thieves — they go everywhere together. OPPOSITE: be at daggers drawn
See also: thick, thief
Farlex Partner Idioms Dictionary

thick as thieves

On intimate terms; very good friends. The use of thick for “intimate” survives mainly in this cliché, which no doubt owes its popularity to alliteration. It was already proverbial, according to Theodore E. Hook, in 1833 (The Parson’s Daughter): “She and my wife are as thick as thieves, as the proverb goes.”
See also: thick, thief
The Dictionary of Clichés by Christine Ammer
See also:
  • (as) thick as thieves
  • thief
  • be (as) thick as thieves
  • have intimate relations with
  • have intimate relations with (one)
  • close as the bark to the tree
  • intimate to
  • intimate to (someone)
  • emotional affair
  • finger (one) as (someone)
References in periodicals archive
? Thick As Thieves - Siwan Morris, Polly Frame, director Roisin McBrinn and Theatr Clwyd's artistic director Tamara Harvey
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"Thick as Thieves" is not sufficiently atmospheric and elegant to make it into a great mood piece, but a talented ensemble elevates the film way above its spotty mise-en-scene.
THICK AS THIEVES
The RTE veterans have been thick as thieves for more than 10 years.
Times get tough for best mates; CAREERS
The sweaty, raucous crowd whooped along with top-10 single Fire's chorus hooks while Thick As Thieves heralded a brief acoustic interlude from the upbeat Where Did The Love Go and Fast Fuse.
KASABIAN
Although Kasabian have yet to name the album - due out this spring - tracks listed so far include Thick As Thieves, Fast Fuse and Underdog.
the Razz: Kasabian mix it up
And he gave the phrase "thick as thieves" a whole new meaning when he nicked a sat-nav system from ANOTHER motor that had been set up as a trap by cops.
P-RAT TRAP! EXCLUSIVE Thief nicked TWICE breaking into 'sting' car
"Madonna and Rupert Everett were thick as thieves," DeCaro says.
DeCaro talks the Talk
Thick as Thieves travelling theatre company present the Tempest FOLLOWING last year's critically acclaimed and award-nominated run at The Hope Theatre in London, the Thick as Thieves Theatre Company bring's William Shakespeare's The Tempest to Wrexham Library on Tuesday, October 11.
One of the Bard's finest
The mates were thick as thieves at a launch party for Sony Ericsson at Baker Street in London on Tuesday.
Stephen: I could be Al Rapone