Noun

1. Customary way of speaking or acting; custom; fashion; manner; behavior; mien; mode; practice; -- often used formerly in such phrases as: at his own guise; that is, in his own fashion, to suit himself.
   • 1924: Aristotle. Metaphysics. Translated by W. D. Ross. Nashotah, Wisconsin, USA: The Classical Library, 2001. Available at: . Book 1, Part 5.

     dialecticians and sophists assume the same guise as the philosopher

2. External appearance in manner or dress; appropriate indication or expression; garb; shape.
3. Cover; cloak; as, under the guise of patriotism.