Third-person singular simple present indicative form of concertina.(verb)
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Use "concertinas" in a sentence
"If you go to Wikipedia you can find out that "As an adhesive, Rabbit-skin glue is used in the production of the bellows of concertinas.""
"Others, the timber-haulers and sawyers, delivered a constant supply of seasoned sawn English walnut trunks, stacked carefully in the yard in big concertinas, sticks separating every plank to keep the air flowing."
"I have 2 button accordions, a small piano accordion, 2 english concertinas (a large one and a small one), and an Anglo concertina."