Although heinous traditionally means evil, it is used by many
teenage girls to describe someone that is so
horribly ugly or disgusting that it is almost evil in itself for that person to look that way.
The word is not just used to describe extremely unattractive people, but it can also be applied to objects--especially clothing
apparel.
Mary: I think she is pretty.
Jess: Are you kidding? I think she's heinous.
Christina: What do you think of this sweater?
Jess: That is the most heinous thing I've ever seen.
Marissa: Do you want to go to the mall tomorrow with me and Johnny?
Jess: Ew!!!! Why do you hang out with him? He is SO heinous!!