10chars an abbreviation for "10 characters." It is used as a method of bypassing 10 character limits in forums when your post would have otherwise been too short.
It's now mostly a joke, however. Posters will be most likely seen just using the number and adding a humorously relevant/silly/sexual substitute for "chars", especially when their post is already above 10 characters.
Gay.
10chars
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Haha... Rick Roll'd muthafucka
10lols
91👍 11👎
A term added to pad short posts on message boards that enforce a ten-character content minimum.
l33t_h4x: lol you got pwnt
n00b-69: fuxx 10char
404👍 107👎
When you're too impatient to wait for a response on a forum thread, you write "bump 10char" to push it to the top of the forum so more people will see it. The 10char part is to meet the requirement of some forums to have 10 characters in a post.
Original poster: What's your favorite Pokemon?
*Five seconds without a response*
Original poster: Bump 10char
New poster: Pikachu.
Original poster: Yay! A response!