Plain English Meaning

Panels that pop up out of the wings to slow the airplane down or help it descend faster. Spoilers also reduce how much lift the wing is producing, which is useful when landing or when you need to come down quickly without speeding up.

Full Definition

Hinged or extendable panels on the wings (and sometimes the fuselage) that, when deployed, increase drag and, in the case of spoilers, also reduce lift by disturbing the airflow over the top of the wing. Speedbrakes are used primarily to slow the airplane or increase descent rate without changing pitch attitude. Spoilers serve the same drag function but are specifically designed to 'spoil' lift, which makes them effective for descent control in flight and for putting the airplane's weight firmly onto the wheels after .