The Collaborative International Dictionary of English v.0.48:

Scavenger hunt \Scav"en*ger hunt\, n.
   a game in which individuals or teams are given a list of
   items and must go out, gather them together without
   purchasing them, and bring them back; the first person or
   team to return with the complete list is the winner. The
   items are sometimes common but often of a humorous sort.
   [PJC]