big-boy pants

Meanings

nounbig-boy pants pl (plural only)

alternative big boy pants

informalpluralplural onlyPull-up underwear worn by a boy during and after toilet training, as contrasted to the diapers worn during infancy.
“We've switched to big-boy pants. No more diapers,” his mom said a little too loud, so Alec would hear.
2000, Timothy A. Buzzard, Guru in a Little Boy Suit, Trafford Publishing, published 2000, →ISBN
2 more examples
Taking the baby from Kidd she snatched the screaming Davey by the wrist and half-carried him up the stairs yelling, "You wanna wear big-boy pants? Big boys wear big-boy pants, but big boys use the potty!"
1983, Randall Wallace, So Late Into the Night, Doubleday, published 1983, →ISBN, page 29
"And so," you continue, "I'm putting your diapers away because you can now wear big boy pants and do your poop and pee-pee in the potty chair all by yourself."
1987, Eleanor Weisberger, When Your Child Needs You: A Parents' Guide Through the Early Years, Adler & Adler, published 1987, →ISBN, page 31
figurativelyinformalpluralplural onlyA notional pair of trousers or underwear worn by a male when acting maturely.
He needs to put on his big boy pants and make the tough choice.
2012 April 12, Alissa Gulin, “Keystone Pipeline: It won't unlock the future”, in The Diamondback, volume 102, number 125, University of Maryland, page 4
2 more examples
If Horwitz is planning on running for office again in the future (and it certainly looks that way), perhaps it's time he put on his big-boy pants and engage in civil discourse.
2011, David H. Hoffman, "Ugly election rhetoric" [letter to the editor], Suburban Life, 25 May 2011, page A8
Even with a broken finger, Wach put on his big boy pants, wrapped his hand, and dominated on the offensive line all game.
2014, "Jewish Community Football League Playoffs and Championship!", The Baltimore Jewish Home, 11 December 2014 - 25 December 2014, Volume 1, Issue 21, page 19
Synonyms: big-boy britches · Antonyms: bitchy pants, grumpy pants, scaredy pants