Noun: An imaginary pass or permission slip, granted by one's spouse, BF, or GF to go out socially with friends.
This colloquial phrase did NOT imply any romantic or sexual encounters. It pre-dated the 2010 comedy film ("Hall Pass") by several decades. This definition relates to adults. This phrase is commonly used by people who attended US schools in the 1960's - 80's.
SYN: see "Permission Slip" and "Kitchen Pass"
Ex: Jeff told Dave that he had two tickets for the middleweight boxing match on this coming Saturday. He asked Dave if he wanted to come to the match. Dave replied, "Let me get back to you on that, I'm not sure if Susan will give me a Hall Pass
to go out this Saturday night."