From adult +‎ -y.


adulty (comparative more adulty or adultier, superlative most adulty or adultiest)

  1. (informal, nonstandard) Characteristically like an adult
    • 2013, Kristen Tracy, Bessica Lefter Bites Back - Page 101:
      And because I knew I was supposed to talk to him like he was an adult, I filtered everything I said and made sure it sounded adulty before it left my mouth.