(1):

(a. / adv.) Without being known; in disguise; in an assumed character, or under an assumed title; - said esp. of great personages who sometimes adopt a disguise or an assumed character in order to avoid notice.

(2):

(a.) One unknown or in disguise, or under an assumed character or name.

(3):

(a.) The assumption of disguise or of a feigned character; the state of being in disguise or not recognized.