NOUN (2)

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;


VERB (1)

1. collapse like a concertina;

The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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 1: collapse like a concertina