1. to lie so badly that, theoretically your pants will burst into flames. popularized by the kindergarten chant, "liar liar pants on fire!".
2. to be painfully gay.
so then i told her i'm puff daddy's personal coke tender, and she bought it. i'm surprised my pants didn't catch fire on the spot.
by Dickie Moist October 7, 2003
Liar Liar Pants On Fire is a phrase that children like to scream at each other whenever they think the other is lying. They also like to scream it at adults who tell them stories about fairies. It is an overall stupid thing to say, since if your pants actually caught on fire when you lied, more politicians would be dead.
Kid: Liar Liar Pants On Fire!
Adult: Shut the fuck up.
Kid: *cries*
by Adam Cecil May 29, 2006
"Liar Liar Pants On Fire" is a playground taunt that is used to indicate each other whenever they think the other is lying.

It refers to the fact "fibbing" is consider naughty, and pants/bottom 'on fire' is an euphemism for spanking.
Child1: Well my dad can pick up a truck!
Child1: Liar Liar Pants On Fire!
by Roguebfl April 14, 2009
In my experience when I was growing up," Liar Liar Pants On Fire" refereed to the ass whipping you would get if your parents caught you lying.You felt like your pants were on fire afterwards
Mom yelled"Liar Liar pants on Fire" when I was caught lying about skipping school.
by Geek Hillbilly June 6, 2016
A Chant normally used by children to indicate they think someone is lying.
The full phrase is "Liar, liar, pants on fire. Hangin' on a telephone wire".
It is a paraphrase form an 1810 poem by William Blake titled "The Liar".
Tom: "I didn't brake that lamp. My brother Dick broke it."

Dick: "Liar, Liar, pants on fire!"
by procadman January 8, 2012
Being from newfoundland, we have a strong British heritage. I always understood it to be a reference to witches burning at the stake. Your pants or skirts would be the first thing to catch fire.
Person on stake while fire burns, sees their pants catching aflame
"Please! I'm Innocent! "
Crowd "liar liar pants on fire
by Newfiegirl April 5, 2017