When a hot girl has skinny legs, forming a gap between her thighs. This would hypothetically allow
one to "cup" her vagina with a hand while she is standing up. In its more moderate form, it results in an upside down
triangle shaped gap, which is also quite hot.
*Not to be confused with the optical illusion created by larger
girls squeezing into tight jeans.
"
Wow, look at the cupability on that
chick." or; "Damn, that girl's
got negative cuppa."