When someone was ugly when they were young and is now sexy/looking good. They have ugly duck syndrome as they believe to be still ugly but are actually very good looking usually works well for the partner who met them when they were ugly. Ugly Duck Syndrome is a good looking person who lacks confidence or releases they are much hotter than they think and there partner but the partner is aware she has ugly duck syndrome.
Much like the tale of the ugly duck who turned in to a swan.
Wow she is so hot and does not realise it, she has ugly duck syndrome.
Man 1: I met a girl who is hot and she actually like me.
Man 2: She must have Ugly Duck Syndrome (UDS)
(n) refers to females who -because something belongs to them, or they created something (a baby) - cannot step back and see that it is hideous-looking and repulsive to most everyone else (and especially men) who look at the same thing.
Named after the medically known fact that the majority of women who birth ugly babies believe that this said baby is absolutely beautiful.
Do you see Tanisha's new baby?
"Yes. Man, is that thing butt-ugly or what? And she keeps going on and on and on about how it's the most beautiful baby that she's ever seen."
She's got Ugly-Baby-Syndrome, for sure! She does the same thing with her hideous-looking shoes too -- she's always wearing some ugly heels and she thinks they're beautiful.
This female can be found normally with a group of extremelyhot girls, and is typically fat, ugly, disgusting, greasy, looks like a train just ran over her face or is just totally hideous.
A situation in which a girl who used to be ugly before puberty becomes hot, but still, in her own mind, she thinks she is ugly.
Often referred to as U.D.S.