When an unattractive, un-groomed female sits on your face until you become short of air, thus making the sound of a Wookie
"Man...I got so drunk the other night, I took a girl home from the club, and she gave me a damn Chewbacca Mask
, man. Ain't that a bitch!"
When you shave your pubes, then later when having sex with a female, ejaculate on her face, then throw the pubes on the ejaculated sperm, leaving the female with a chewbacca mask.
Maurice pulled out his bag of pubes, right as he gave Lindsay a facial, then proceeded to sprinkle the pubes on her face, leaving her with a chewbacca mask.