look up any word, like sparkle pony:
 
1.
[x]
Brackets that represent a filled tick-box. Hence the writer is asserting that the statement following the brackets is true, or wants to highlight the presence of something or other.

{x} is the opposite of { }, an unchecked tick-box which means the statement is false or missing.

Multiple tick-boxes are often strung together, like a check-list of true and false statements.

(Note - curly brackets are used in the examples, since urbandictionary uses square brackets to denote links. However in real usage, square brackets should always be used.)
Quote: "I just really love bananaz. They are the best fruit by miles!!!1!"

{x} bananaz
{x} fruit experts itt
{ } OP has better things to do than posting this shiz

x
by Tickboxman August 12, 2010
 
2.
[X]
X = Means Sabotage.
X has just pwned you!
by SabotageX June 21, 2005