I. con ‧ cer ‧ ti ‧ na 1 /ˌkɒnsəˈtiːnə $ ˌkɑːnsər-/ BrE AmE noun [countable]
[ Date: 1800-1900 ; Origin: concert ]
a musical instrument like a small ↑ accordion , that you hold in both hands and play by pressing in from each side
II. concertina 2 BrE AmE verb [intransitive] British English
if something concertinas, it folds together on itself