adj.
added to an existing or usual amount or number.
adv.
- to a greater extent than usual.
- in addition.
n.
- an item for which an extra charge is made.
- an extra item.
- a person engaged temporarily to fill out a crowd scene in a film or play.
- Cricket a run scored other than from a hit with the bat, credited to the batting side rather than to a batsman.
Etymology
C17 (as adj.): prob. a shortening of extraordinary, suggested by similar forms in Fr. and Ger.