Grool is derived from “girl drool”.
As opposed to what is sounds like, it does in fact not refer to saliva running from a girls mouth, but to the vaginal fluids running from a girls vulva.
It is the vagina “drooling”, or in other words, getting wet, when the woman is sexually aroused. The grool may be clear or creamy, varying from woman to woman.
Not to be confused with “squirting” which is another concept completely, involving female ejaculation.
Another meaning can be great + cool put together, making “grool”.
Origin of the term
“Girl drool” and “grool” became a thing about a decade ago, around 2010. It was made popular by porn videos.
“Grool” as a reaction (great + cool) was originally said by the main role Cady in the movie Mean Girls, accidentally mixing the two words while talking to an attractive boy.
Spread of the term
Porn sites has numerous “grool” videos. A very wet woman is synonymous to a very aroused woman (in the porn world), and obviously aroused women is a huge turn-on for heterosexual men.
Multiple subreddits are dedicated to the concept, and even the concept of “grool-tasting” – which is, as the name indicates, tasting grool – has its own subreddit.
The reaction “grool” is used as a fresher version of its components “cool” and “great”.
It is also used in situations where someone fucked up in a conversation, because they were nervous, just like the main character did in Mean Girls.