Source : Webster's Revised Unabridged Dictionary (1913)

Concertina \Con`cer*ti"na\, n. [From It. concerto a concert.]
   A small musical instrument on the principle of the accordion.
   It is a small elastic box, or bellows, having free reeds on
   the inside, and keys and handles on the outside of each of
   the two hexagonal heads.

Source : WordNet®

concertina
     n 1: coiled barbed wire used as an obstacle
     2: free-reed instrument played like an accordion by pushing its
        ends together to force air through the reeds
     v : collapse like a concertina