Noah Webster's New International Dictionary of the English Language

1. (n.) 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. (n.) That which disguises; a pretext or subterfuge.

3. (n.) A festive entertainment of dancing or other diversions, where all wear masks; a masquerade; hence, a revel; a frolic; a delusive show.

4. (n.) A dramatic performance, formerly in vogue, in which the actors wore masks and represented mythical or allegorical characters.

5. (n.) 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. (n.) In a permanent fortification, a redoubt which protects the caponiere.

7. (n.) A screen for a battery.

8. (n.) The lower lip of the larva of a dragon fly, modified so as to form a prehensile organ.

9. (v. t.) To cover, as the face, by way of concealment or defense against injury; to conceal with a mask or visor.

10. (v. t.) To disguise; to cover; to hide.

11. (v. t.) To conceal; also, to intervene in the line of.

12. (v. t.) To cover or keep in check; as, to mask a body of troops or a fortress by a superior force, while some hostile evolution is being carried out.

13. (v. i.) To take part as a masker in a masquerade.

14. (v. i.) To wear a mask; to be disguised in any way.