a musical instrument resembling an accordion but having buttonlike keys, hexagonal bellows and ends, and a more limited range.

concertina wire.

to fold, crush together, or collapse in the manner of a concertina

The car concertinaed when it hit the truck.

to cause to fold or collapse in the manner of a concertina.

of, pertaining to, or resembling a concertina

concertina pleats.