Merriam-Webster's Collegiate® Dictionary, 11th Edition
CONCERT
I. noun
Etymology: French, from Italian concerto, from concertare
Date: 1571
agreement in design or plan ; union formed by mutual communication of opinion and views, musical harmony ; concord , a public performance (as of music or dancing), concert adjective
II. verb see: certain
Date: 1652
transitive verb to make a plan for , to settle or adjust by conferring and reaching an agreement , intransitive verb to act in harmony or conjunction