(noun)In ice climbing, a large icicle shaped chunk of ice crashing to the ground. Most commonly associated with spear shaped ice chunks, however any chunk of ice falling to the ground can be known as a belayer slayer.
Climber: Dude, I went climbing the other day.
Climber buddy: Gnarly dude.
Climber: It was awesome until I came across a belayer slayer.
Climber buddy: Sick, everyone alright?
Climber: Yeah, it's all good.