When you get judged by the age you are. Mostly young or old people.
" Do you want to hang out with Sam?"
"No he's 12."
"Why not?"
"He's going to ruin it for us!"
"Don't be ageist."
by Black Brightness April 1, 2016
Someone who discriminates and stereotypes aganist a person based on their age. In short, a wanker.
1: Children are unable to understand politics, they just repeat whatever they hear or are told.

2:(snorts) Ageist.
by QueenJaneApproximately March 6, 2010
Being ageist by discriminating someone because of their age.
"Everything what young people do, is sit in front of a computer and be lazy. Y'all would die if a world war would happen."

"Grandpa, please stop being ageist and judging my whole existence and everything I do, only by my age."

or

"Oi, I'm not putting my life into this lil' brats hands!"

"Sir, please stop being ageist. This is your surgeon, trying to save your life..."
by Gen69 February 10, 2021
When you are prohibited from something for not being a certain age.This is commonly found with dangerous actions, but can also be seen with stupid things for no reason.
I am obsessed with Scholastics, which is a school activity that resembles Jeopardy. Was on the panel ready to compete, the Judges kicked me off of the panel for not being a senior. Isn't that so ageist?
by Underappriciated November 22, 2011
When someone discriminates against another based on age
Mike: "We couldn't get into the concert even though we already paid for the tickets."
Susan: "Why not?"

Mike: "It's 18+ those people are ageist!"
by ihavetopee August 26, 2017
When somebody uses age to judge, discriminate or stereotype against another when in fact age is completely irrelevant.
User 69: *says something immature/inappropriate in twitch chat*
Moderator: User 69, how old are you?
User 69: 22, why?
Moderator: That's funny, I'm 17 and even I know better not to say something like that. Please be more mature next time.
User 69: Wait wait, so you're saying that if I were 17 and you were 22, you'd be fine with it? That's hella ageist my dude.
by UwUltimateDoge July 19, 2021