A girl with just a little bush. The bush is expected to be clean and maintained ... a little turf on the field. Reminiscent of when a girls pubs have grown in for the first time and has never been molested by the shaver.
Specifically, the word is used to refer to a young girl, late junior high school through high school, that is expected to have or has a bush as described above. The use of squirrel is considered already pluralized when referring to a pack of girls.
Jenni's totally a squirrel, time to give her my nuts.
Tony "Tone": Yo, Ron, you think she a squirrel?
Ron: Yea man, she wearing yoga pants. You can see the squirrel right up front.
Wooderson: That's why I love dem squirrel's. I get older, they stay the same age.
Timmy: Mommy, what's a squirrel?
Mommy: Here Timmy take a look.