Unfuckable is the penis useless to fuck, not because the lack of erection, but due to its very small size, equal or inferior to 4 cm ( or 2 inches ) when erect, turning impossible the intercourse in the vagina ( ups and downs), to achieve the orgasm. In such cases, to obtain it, is necessary to use a penis pump to masturbate. The same occur with the buried ( in the pelvis) penises. Many times, the improper size refers only to the length of the organ, not the girth, that can be large ( only a big head outside the pelvis, but totally useless to move ).

Group of under age boys or girls ( less than 18 y.o. in most countries and states of USA ) forbidden to fuck by law.

adj; something that is incapable of being fucked, due to repulsive appearance, physical infeasability or some social or behavioral inhibition.

a chick that is so hot that you know she will never even let you near her

Some thing or situation that is so cool, so very perfect, so impressive, that no one could ever concieve of it as fucked, or fucked up, or all fucked up; or say about it "Fuck that." It's too good. It can't be fucked. It's unfuckable. From the Russian nev'yebenno.

An extremely ugly woman/girl that nobody wants to have sex with.

A fat black girl that is so grossly overweight nobody would date her, much less have sex with her.