Meaning of the word "be (as) thick as thieves" in English

What does "be (as) thick as thieves" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

be (as) thick as thieves

US /bi əz θɪk əz θiːvz/
UK /bi əz θɪk əz θiːvz/
"be (as) thick as thieves" picture

Idiom

1.

to be very close friends and share secrets, often in a way that excludes others

Example:
Those two have been as thick as thieves since childhood.
The new neighbors are already as thick as thieves with the family next door.
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