unconventional beauty 

Somebody who's appearance does not conform to conventional beauty standards, but can still be considered attractive.

lily cole is an unconventional beauty

unconventional beauty by Cadet Ruby March 20, 2019

unconventional beauty 

someone who is not considered beautiful but looks pretty gorgeous in their own unique way

a person may not be very beautiful lookswise, but maybe very charming, she's referred to as an unconventional beauty

unconventional beauty by dakssavasere November 29, 2010

unconventional beauty 

Sometimes used in a sarcastic way to indicate someone who is not very beautiful at all.

I do not understand why I get hit on by gay men more often than straight women, since men are supposed to be the one driven by appearance... For those of you who are unaware, I am of an unconventional beauty.

unconventional beauty by Oxymoronica December 6, 2006