Pronunciation: (u-kôr'dē-un),[key] —n.Music. 1. Also called piano accordion. a portable wind instrument having a large bellows for forcing air through small metal reeds, a keyboard for the right hand, and buttons for sounding single bass notes or chords for the left hand.
2. a similar instrument having single-note buttons instead of a keyboard.
—adj. having a fold or folds like the bellows of an accordion: accordion roof; accordion panel.
—v.i. 1. (of a door, roof, or other covering) to open by folding back or pressing together in the manner of an accordion: The roof of the car accordions to let in sunlight and fresh air. 2. to fold, crush together, or collapse in the manner of an accordion.
—v.t. to demolish by crushing together lengthwise: The impact accordioned the car beneath the truck.