icebreaker

noun3

1. •
   A ship designed to break through ice so that it, or other ships coming behind, can navigate on frozen seas.

   • The steel hulls of ice-breakers are much thicker than those of standard vessels.
2. •
   A lively song and dance routine at the start of a musical.
3. •
   (figurative) A game, activity, humorous anecdote, etc., designed to ease tension and encourage interaction among individuals in a situation where they do not know each other well.

   • The new college hallmates were awkward with each other at first, but after a game of charades as an icebreaker, they were laughing like old friends.