Doing something that you know you shouldn't even when your best friend tells you shouldn't.
An Example of this Beavering be meeting a guy on the internet, and meeting him after dark and alone. Or meeting a person for a "date" for the first time and inviting them to your house and telling them they have to leave by four.
When you think it is kinky to go down on a chick that never shaves her vagina.
Tony: "My girl never shaves her vagina; I refuse 'Beavering'!"
Carl: "That's so disgusting dude! You know what I did that hooker I picked up last week? I donkey punched her because she needs to shave that twat"