1. An attendant or servant.
2. A knight's page.
3. A rascal; a knave.
What a brazen-faced varlet art thou !
A Shakespearean insult that is defined by the character of Thersites in the comedic tragedy, Troilus and Cressida, as a "masculine whore" (5.1.17).
In other words, this is a 17th Century term for a manslut.
Thersites: Prithee, be silent, boy; I profit not from thy talk. Thou art said to be Achilles' male varlet.
Patroclus: Male varlet, you rogue! What's that?
Thersites: Why, his masculine whore.
(Troilus and Cressida, Act 5 Scene 1, lines 13-17)