Twenty-Nothing- noun: Underpaid, overeducated young professionals willing to endure whatever it takes - including but not limited to, daily beratement, humiliation and throwing of objects from their superiors, and mockery from their much more well-paid college friends who got 'real jobs' after graduation - in order to achieve their entertainment industry dreams.
"That twenty-nothing has a law degree and an MBA from Yale, yet works 12-hour days at WME for minimum wage because she thinks she'll be a Hollywood exec one day."
Someone who is 20 years old. Implies he or she is no longer a teenager yet not old enough to drink or party yet.
Wait, Joe can't party with us yet, he's still a twentynothing.