A language in which numbers and symbols are put together to look like letters. Some people create their own 1337 letters and it makes them look more 1337 by fellow 1337-speakers. Here is an alphabet of 1337 letters I know and have created:

A: 4 or l\ or ^ or @ or /\ or /-\
B. l3 or 8 or ß or ]3 or l:
C: ( or < or © or ¢
D: l) or l> or ])
E:3 or £
F: l= or # or ƒ
G:6 or 9
H: # or l-l or (-) or !-! or }-{ or }{ or l+l or )+( or !+! or }+{
L: 1 or ! or ][
J: _l or _/
K: l< or l( or l{ or l<=
L: l_ or ! or 1
M: l\/l or /\/\ or l\l\ or ^^
N: l/l or /\/
O: 0 or () or <> or * or ø or Ó or °
P: l* or l> or |D or l^ or l+
Q:& or (\) or ¶
R: l2 or ®
S: 5 or $ or §
T:+ or 7
U: l_l or /_/
V: \/
W:|/\| or \/\/ or |/\/ or \/\|
X: >< or }{ or :-:
Y: ¥
Z: 2