0 a piece of thick soft material used in sports, etc. so that someone can jump or fall from a height without hurting themselves: --
The story goes that in one performance of Tosca, a stage manager replaced the crash mat that cushions the heroine's suicidal plunge from the castle walls with a trampoline.
A cast member broke his ankles when he missed a crash mat in a high-wire fall at the film studio.
Not too many people hurt themselves falling off a trapeze because there are crash mats and supporters there to protect them.
In bouldering, falls don't usually result in serious injury, particularly if you use a crash mat.