plural of proof house

A proof designed to monitor the progress of printing, similar to an artist's proof.

plural of proof leaf

(obsolete) A proof sheet (page of proofed text)

(firearms) A mark stamped on a gun to show that it has been tested successfully.

plural of proof mark

Of a play, etc.: resistant to negative responses from the audience; popular with everybody.

(less common) Alternative form of the proof of the pudding is in the eating

A psychological and social phenomenon wherein people copy the actions of others if unsure how to behave.

(informal, humorous) Incapable of being misused even by the stupidest or most careless of users.