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 worlds vain mask. (Milton)
4. A dramatic performance, formerly in vogue, in which the actors wore masks and represented mythical or allegorical characters.
5. 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. In a permanent fortification, a redoubt which protects the caponiere. A screen for a battery.
7. (Science: zoology) The lower lip of the larva of a dragon fly, modified so as to form a prehensile organ. Mask house, a house for masquerades.
Origin: f. Masque, LL. Masca, mascha, mascus; cf. Sp. & pg. Mascara, It. Maschera; all fr. Ar. Maskharat buffoon, fool, pleasantry, anything ridiculous or mirthful, fr. Sakhira to ridicule, to laugh at. Cf. Masque, masquerade.