Mask n.
 1. A cover, or partial cover, for the face, used for disguise or protection; as, a dancer's mask; a fencer's mask; a ball player's mask.
 2. That which disguises; a pretext or subterfuge.
 3. A festive entertainment of dancing or other diversions, where all wear masks; a masquerade; hence, a revel; a frolic; a delusive show.
    This thought might lead me through the world's vain mask.   --Milton.
 4. A dramatic performance, formerly in vogue, in which the actors wore masks and represented mythical or allegorical characters.
 5. Arch. A grotesque head or face, used to adorn keystones and other prominent parts, to spout water in fountains, and the like; -- called also mascaron.
 6. Fort. (a) In a permanent fortification, a redoubt which protects the caponiere. (b) A screen for a battery.
 7. Zool. The lower lip of the larva of a dragon fly, modified so as to form a prehensile organ.
 8. A person wearing a mask; a masker.
    The mask that has the arm of the Indian queen.    --G. W. Cable.
 9.  Sporting The head or face of a fox.
 Mask house, a house for masquerades. [Obs.]
 Death mask, a cast of the face of a dead person.