OED:

1. a. One of the shaped pieces of canvas or other strong textile
material fastened to the masts, spars or stays of a vessel, so as to
catch the wind and cause it to move through the water. Also occas. a
similar apparatus for propelling a wind-driven carriage.

b. transf. Applied to the wing of a bird. poet. Also techn. in
Falconry, the wing of a hawk.


c. transf. Applied to something that is spread out like a sail, or
that catches the wind.


d. Aeronaut. Applied to a flat aerodynamically structured part of
an aircraft. Obs.

Note "c".

Cheers MC