Top definition
The act of inserting multiple fingers at least second knuckle deep into your partners rectum, optimally by surprise. Often done during fellatio or cunnilingus.
Sabrina is great at knucklebutting, she can get third knuckle deep before you even notice.
by SasquatchSB October 04, 2010
Get the mug
Get a Knucklebutting mug for your Aunt Nathalie.