(Adj)
1. Someone who shields themselves from fun too often. Esp. when rejecting propositions for weak reasons.
Person 1: Hey, wanna go to that new club?
Person 2: No thanks, I have a project I need to get started.
Person 1: Don't be lame, you can work on it tomorrow.
Noun: A responsible homebody, introvert, who is content with work, and domestic life. Someone who likes to stay home and rather than go out and act a fool or spend wrecklessly.
Adjective: Descriptive if said qualities in a person.