muffler
n.a slang word for a woman's vagina. It is a very crude and offensive term that people use to be rude or shocking.
n.a highly offensive and vulgar slang term for the female genitalia. Used primarily in informal, crude, or shock-value contexts; considered extremely inappropriate for professional or polite discourse.
“He used a crude word like 'muffler' to insult her.”
“The comedian's set was filled with offensive slang, including the use of 'muffler' to describe a woman's anatomy.”
“While the term 'muffler' is occasionally used in specific regional dialects to refer to a car part, its application to female anatomy is strictly limited to vulgar or degrading speech.”
From muffle + -er.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.