Mask, n.
Etymology: [F. masque, LL. masca, mascha, mascus; cf. Sp. & Pg. máscara, It. maschera; all fr. Ar. maskharat buffoon, fool, pleasantry, anything ridiculous or mirthful, fr. sakhira to ridicule, to laugh at. Cf. Masque, Masquerade.]
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. Bacon. 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 more senses
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. (Zoöl.)
The lower lip of the larva of a dragon fly, modified so as to form a prehensile organ. Mask house, a house for masquerades. [Obs.]
2 other Webster entries under this spelling
Mask, v. t. [imp. & p. p. Masked; p. pr. & vb. n. Masking.]
1. To cover, as the face, by way of concealment or defense against injury; to conceal with a mask or visor. They must all be masked and vizarded. Shak.
2. To disguise; to cover; to hide. Masking the business from the common eye. Shak.
3. (Mil.) (a) To conceal; also, to intervene in the line of. (b) To cover or keep in check; as, to mask a body of troops or a fortess by a superior force, while some hostile evolution is being carried out.
Mask, v. i.
1. To take part as a masker in a masquerade. Cavendish.
2. To wear a mask; to be disguised in any way. Shak.
Shades of meaning
Fernald has no entry of its own for mask; he lists it under hide, pretense.
He lists it without comment; the entries above explain its neighbors.