a structure in a hollow organ (like the heart) with a flap to insure one-way flow of fluid through it
internal-combustion engine having both inlet and exhaust valves located in the cylinder head
device in a brass wind instrument for varying the length of the air column to alter the pitch of a tone
control consisting of a mechanical device for controlling the flow of a fluid
one of the paired hinged shells of certain molluscs and of brachiopods
the entire one-piece shell of a snail and certain other molluscs
