"Leet speak" is an Internet slang language in which certain letters, usually vowels, are replaced by numbers and symbols to form a code. It was originally developed in the 1980s by hackers, but is now more commonly used in chat rooms and by online gamers. Leet speak has also been used to circumvent filters that bar certain words (e.g., porn has become pr0n). In its simplest form, just four vowels are replaced (A=4, E=3, I=1, O=0), so the word leet becomes l33t. Although leet speak is based on the English language, many phrases and words are unique to it. According to the BBC, some of the most commonly used leet speak words and phrases are:
pwnd: to have been beaten
w00t: used as a term of elation
l3wt: treasure; a misspelling of "loot"
ph33r: fear (e.g., "Ph33r m3!")
j00: you (e.g., "j00 d34d f00")
Stephen Leacock (1869-1944)