octantal
Octantal is 18, but also a fancy way to say you're old enough to drink, lie, and sign contracts you'll regret.
My brother turned octantal and now he's legally allowed to ruin his life.
The bartender asked, 'Are you octantal yet?' I said, 'No, but I'm close.'
My mom said, 'You're octantal now, so stop acting like a toddler.'