It's the contraction of the words "it is" so it's the same as "it's".

"iTz" is a statement of self-misconception that putting things like multiple x's, MLG, "legit", and "iiTz" in combination for a pseudonym will make one totally badass. Generally, these specimen are annoying prepubescent teenagers, or self-righteous douchebags of an older literal age (versus an older mental age).

Warning: Do not attempt to interact with these species (one specimen might be identified as something along the lines of "iiTz lEGiT MLG pRoO xXx"), as they will often challenge you to a one-verse-one duel. Denial to the challenge will result in a incessant condescending speech explaining (without logical sense) why you are a small cat.

Initials standing for "in the zone", which was a popular Halo 2 clan.

Often mispercieved as meaning "it's" by the people that use it in Halo 3 and elsewhere today.

Incorrect spelling of the word "It's."

Commonly seen amongst the Halo community, often used by people who have the mindset that they are MLG Pro, and will step to any noob who thinks they can win a 1v1 match.

a game played to find a persons hot spot

1) Someone on urbandictionary who is very egotistical.

2) Often used to replace the word 'its' because it is considered 'cool' by many stupid, chilidish, insecure, and annoying people.

Don't try to define my name you jerks.