Definition of mask:
, or partial cover, for the face
, used for disguise or protection; that which disguise
s; a pretext or subterfuge
"a dancer's mask; a fencer's mask; a ball player's mask"
, as the face, by way of concealment
or defense against injury; to conceal with a mask or visor; to disguise
; to cover; to hide
"to mask a body of troops or a fortess by a superior force, while some hostile evolution is being carried out"