Leetspeak

Leetspeak (aka 1337 speak) is originally a form of language used by black hat hackers to communicate to each other. Now, it is more often than not used as a form of shorthand or sarcasm while typing.

Of historical note, however, is that early on in classic World of Warcraft, the language filters between factions did not change numbers and symbols, only letters. This allowed for communication and, more frequently, insults to be shared between Alliance and Horde players. However, this feature was eventually patched in order to better maintain the design notion of distinctiveness and rivalry between the factions.

Alphabet

 * A - 4, @
 * B - 8, 6, 13, |3
 * C - ¢, <, (
 * D - |), [), ol
 * E - 3
 * F - 1=, 1#, |#, |=
 * G - 6
 * H - #
 * I - !, 1, |
 * J - _|
 * K - |<, ]{
 * L - 1, |_, |, !
 * M - /\/\, ^^, |\/|
 * N - |\|
 * O - 0
 * P - |*
 * Q - 9,
 * R - 12, |2
 * S - 5, $
 * T - 7, †, +
 * U - |_|
 * V - \/
 * W - \X/, \v/, \/\/
 * X - ><
 * Y - `/
 * Z - 2

Also known as:
 * Hacker
 * L33T
 * 1337
 * HaXXoR
 * Geek speak
 * etc.

The method of adding numbers and symbols to replace letters in words.

Th3 m3+h0d 0f 4dd1n6 nUmb3RZ 4nd 5Ymb0lZ 2 R3pl4c3 l3++3RZ 1n w0Rd5.

Examples of variations:
 * W0Rld 0f W4RcR4f+
 * \/\/ 0 R 1 |)  0 |=   \/\/ /\ R ( R 4 |= 7