The term Pube Monster is used in association with a shower or general plug hole which is filled with wiry hair most likely from from the pubic region of a large beast/monster. While the likelihood of a beast/monster taking a shower in your house is slim, the sheer mass of hair plugging the hole strongly points in the direction of this....or a person who needs to shave their bush.
Holy moly! Looks like the pube monster has his the shower again!
Why can't the friggin pube monster use a different shower or just buy a bloody razor and give her bush a shave!
Jeremy: Hey dude, do you know Heleena?
Fred: Oh shit man, yeah I do! She's that damn pube monster!