thick as thieves 

to be tight or best friends with someone

josh and maddy are thick as thieves fool

thick as thieves by jsack January 20, 2009

thick as thieves 

A special bond people have for each other.
Derived from the idea of "partners in crime".

Ant and Chris, having attended boarding school together, were thick as thieves.

thick as thieves by DDA September 6, 2005

Thick as Thieves 

People who are good friends.

Ant and Chris, having attended boarding school together for so many years, were thick as thieves.

Thick as Thieves by DDA July 18, 2008

Thick as Theives 

Phrase referring to two or more people who are very tightly connected with one another.

People who trust each other completely and will often confide deep secrets in each other.

"So Bobby and Joey know each other pretty well?"
"Oh yes, since third grade, thick as theives those two."

Thick as Theives by ACG2x December 30, 2004