From Longman Dictionary of Contemporary Englishldoce_001_baccordionac‧cor‧di‧on /əˈkɔːdiən $ əˈkɔːr-/ (also piano accordion British English) noun [countable] 
APMa musical instrument like a large box that you hold in both hands. You play it by pressing the sides together and pulling them out again, while you push buttons and keys. —accordionist noun [countable]
APMa musical instrument like a large box that you hold in both hands. You play it by pressing the sides together and pulling them out again, while you push buttons and keys. —accordionist noun [countable]Examples from the Corpus
accordion• From Arty's room came the sound of an accordion.• The older man plays an accordion, and the younger one plays a tin whistle in the musical interlude.• A man standing under the trees a little way off had produced an accordion and begun to play.• He was carrying four thick brown cardboard accordion folios tied with faded red ribbons.• The prototype antenna popped from its carrier like a jack-in-the-box, and its three 92-foot accordion struts inflated as planned.• With the lights dimmed, a solo accordion played a brief, preliminary waltz.• Except, of course, their love for the accordion.• Water piped out from the accordion folds.Origin accordion (1800-1900) German akkordion, from akkord “chord”, from French accord 