What is the meaning of Concertina?

A musical instrument, like the various accordions, that is a member of the free-reed family of musical instruments, typically having buttons on both ends.

Something resembling a concertina, such as a folded book, a bus door or a set of picture frames that are folded together.

Coiled barbed wire for use as an obstacle.

A type of booklet label, consisting of up to 32 pages of booklet as an insert.

to become compressed into a shape reminiscent of a concertina

to be drawn closer and farther apart repeatedly, or up and down, as if situated on a working concertina's folds

concertina

concertina (coiled barbed wire)

concertina

Source: wiktionary.org