A 12-year-old is typically used as a condescending generalization for someone nieve, immature, or weird on the internet.

a phrase used to specifically describe when you are suddenly surrounded by foul-mouthed, pre-pubescent children who probably are between 6th and 9th grade. Often have squeaky, non-threatening voices and colorful streams of language.

People that oftentimes get defensive about their age because of the stereotype given out on the internet, and try to act more mature then they actually are to make themselves seem not as bad

A rarity according to MicroSoft.

Someone who wanks to YouTube videos.
Ex.
-Christian 12 year old: Hey, do you want to finish the castle on our Minecraft server?
-All regular 12 year olds in unison: No, I'm going to go watch some YouTube videos then go to bed.

Short annoying little shits that get way to close and talk to much. These little fuckers just got potty trained and forget they aren't wearing diapers