\Vent"ail\, n. [OF. ventaille, F. ventail. See
{Ventilate}, and cf. {Aventail}.]
That part of a helmet which is intended for the admission of
air, -- sometimes in the visor. --Spenser.
      Her ventail up so high that he descried Her goodly
      visage and her beauty's pride.           --Fairfax.