plain Jane
A female who is not considered physically attractive by societal standards. Betty always felt like she was a plain Jane, so she was very surprised when the most handsome boy in school asked her to be his prom date.
plain Jane
an unattractive girl or woman. 2002 Guardian [The film] assembles its stereotypes (the sexy exchange student, the plain Jane who's really a fox, the jock who is only dating her for a bet) then proceeds to gunk them all with a ton of scatalogical prankery.
a plain ˈJane
(disapproving) a girl or woman who is not very pretty or attractive: She was a shy girl, who always thought of herself as a plain Jane.