ice-breaker

/AY1 S B R EY0 K ER0/
noun
  1. 1

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

    โ€œThe steel hulls of ice-breakers are much thicker than those of standard vessels.โ€

  2. 2

    A game, activity, humorous anecdote, etc., designed to relax a group of people to help them get to know each other.

    โ€œThe 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.โ€

  3. 3

    A lively song and dance routine at the start of a musical.

Source: https://en.wiktionary.org/wiki/ice-breaker, https://en.wiktionary.org/wiki/icebreaker