This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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n. A control surface on an airplane that combines the functions of an elevator and an aileron.

n. a moveable surface at the trailing edge of a tailless airplane (such as the space shuttle) that provides pitch and roll control

"A special schedule of elevon position with respect to velocity is followed to protect the wings from excessive loads and to hold the body flap and rudder/speed brake in place."