'Waiting room' is a room for waiting. 'Waiting' is a gerund here, and it is used as one noun modifying another. It's the same as 'dining room' or 'family room' or 'play room.'
In your examples -- waiting man,waiting girl,waiting answers -- 'waiting' is the present participle describing the noun: the man is waiting, the girl is waiting, and the answers are waiting.
I don't know any meaning for 'waiting ages.' Is there any context for this phrase?