放空

to relax completely / to empty one's mind / (finance) to sell short / (of a commercial vehicle) to travel empty (no cargo or passengers) / to deadhead

to put / to place / to release / to free / to let go / to let out / to set off (fireworks)

empty / air / sky / in vain

to empty / vacant / unoccupied / space / leisure / free time

(lit.) to fire blank shots / (fig.) to be all talk and no action / to shoot one's mouth off / to make empty promises

to coast along in neutral gear (in a car) / (coll.) to go commando