Twirty
Age of a woman in her late twenties or mid thirties. Women of this age are seen as continuously defying their actual age.
That frat boy hit on me because he has no idea I'm twirty!
Twirty-Something
A woman who has passed the lower numbers of the Twirty age range but is still continuously mistaken for a whole lot younger.
Even though we twirty-somethings felt out-of-place at the kegger, we were still getting hit on so hard we had bruises.