- The fruit of the oak, being an oval nut growing in a woody cup or cupule.
- [Naut] A cone-shaped piece of wood on the point of the spindle above the vane, on the mast-head.
- [Zoöl] See Acorn-shell.
Etymology: AS. æcern, fr. æcer field, acre; akin to D. aker acorn, Ger. ecker, Icel. akarn, Dan. agern, Goth. akran fruit, akrs field; -- orig. fruit of the field. See Acre