Definition of "icebreaker"

My father's Bonneville was cutting its way toward us like an icebreaker moving through my whole state of consciousness.

2004, Martin Torgoff, Can't Find My Way Home […] , Simon & Schuster, page 11

The key purpose of an icebreaker is to introduce your group members to each other and to introduce your training session topic. A well-planned icebreaker ensures that a training session will start with more involvement and focus.

2011, Elaine Biech, chapter 11, in The Book of Road-Tested Activities, John Wiley & Sons

At the moment the curtain went up there had to be a lively ensemble number of principals and chorus singing and dancing, the traditional “icebreaker” that also covered up the noise of late-arriving ticket holders getting to their seats.

2014, Maggie Davis, Stage Door Canteen