The definition of plain jane is a girl that is plain, ordinary and not especially memorable or special.
An example of plain jane is a woman who is not beautiful or exceptionally smart.
a plain, dowdy, unremarkable woman or girl
- plain, drab, dull, etc.: plain-Jane looks
- basic or simple; ordinary; unremarkable
Origin of plain-Jane; from plain Jane
Lacking adornment or pretension; basic or simple.