Just launched! Learn slang while watching funny vids: urbandictionary.tv
1. putting out
to engage in sexual intercourse (usually penile-vaginal) when expected to, according to social conventions such as dating
It was already the second week they were going out and Chris was starting to lose interest in Ashley because she wasn't putting out.
2. Putting out
When someone is offering themself in any way the opposite sex wishes.
Bob - "Dang, she ugly! Why is she so popular!?"

Dave - "Ain't you heard about her. She's putting out to everyone"