A person or thing that is in excess of the usual, proper, or prescribed number. The theater company hired several supernumeraries to fill out the crowd scenes in the play.
An actor without a speaking part, as in a crowd scene in a play or film; an extra. The director instructed the supernumeraries to move to the left side of the stage during the battle scene.
A person who is present in a situation but not essential to it. As a supernumerary at the meeting, she was there to observe rather than participate.
An additional body part, especially an extra tooth or digit, occurring beyond the usual number. An X-ray revealed two supernumeraries behind the patient's upper incisors.