to make a sharp noise by moving your second or third finger quickly against your thumb, to attract somebody’s attention, or to mark the beat of music, for example打榧子,弹指头(捻拇指作响)
He snapped his fingers for the waiter to bring more wine.他啪的一声让服务员多拿些酒来。
He snapped his fingers and the waiter came running.他打了个响指,服务生快步走来。