A form of encryption commonly used these days by the geek/internet-friendly crowd as a standard for personal password compliance with stricter unix-style password requirements.
Basically, what commonly happens is one is overflowed with many, many passwords to keep track of. Especially if one is a university student. Even moreso if one is an internet user1. So people tend to have a very small set of passwords. Sometimes, these passwords are less than secure, especially by the stricter standards some unix boxes will enforce2.
So, enter leet encoding. This is commonly an encoding technique applied to either legacy passwords or sight-generated passwords. Basically, you take said insecure password, and replace every applicable letter with its alternate equivalent in the leet alphabet.
Quick, simple, easy to remember, and most importantly, will make the command prompt stop harrassing you. Of course, this isn't a good way to salvage a previously compromised password, as it's a very easy mental filter to apply for anyone, but as long as the source password wasn't blatantly obvious3, it'll do, pig. It'll do.
Which I'll assume you are, seeing as you're on everything2
Enfocing such rules as: Cannot be a straight-up dictionary
word. Should have lower-case, upper-case, numerics, and special characters
Like, say, being the same as your user account name. Dolt.