acorn /āˈkörn/ noun The fruit of the oak ORIGIN: OE æcern; form influenced by confusion with corn1 and perh oak (Scot and N Eng aik, OE āc) āˈcorned adjective aˈcorn-cup noun The woody cup-shaped part of an acorn that holds the nut aˈcorn-shell or aˈcorn-barnacle noun A sedentary crustacean of the genus Balanus acorn worm noun Any of various wormlike sea-animals (enteropneusts) of the Hemichordata which have a proboscis and collar somewhat like an acorn in shape |