If you are in disguise, you are not wearing your usual clothes or you have altered your appearance in other ways, so that people will not recognize you.
to change your appearance so that people cannot recognize you 假扮；装扮；伪装
~ sb
The hijackers were heavily disguised.
劫持者伪装得严严实实。
~ sb as sb/sth
They got in disguised as security guards.
他们装扮成保安人员混了进去。
~ yourself (as sb/sth)
She disguised herself as a boy.
她女扮男装。