Mask \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.

Source: Webster's Revised Unabridged Dictionary (1913)