1.NounA brake (slowing device) that is operated pneumatically (by air pressure).
"The powerful airbrake of the truck quickly brought it to a stop."
2.NounA movable control surface that extends to increase drag without affecting lift (unlike a spoiler); a device that provides aerodynamic braking.
"The BAe 146 and Fokker 100's tailcone-mounted airbrakes allow them to slow down quickly for steep approaches without experiencing the lift degradation seen with spoiler-only aircraft."