If you worked at Express in the '90s, you'd have to learn your phats from your fines in an employee handbook called Express You! Street Verbage Guide .
In an attempt to make their employees downright dope, mall clothing chain Express gave workers this handbook/dictionary that decoded the language of the youths.
Note the incorrect spelling — verbage — which should read verbiage.
Source: theawl.com
The book of terms has some familiar ones — phat, bomb, mad, ill, lame, etc. — but others are a bit more obscure. For the full list, you can read and study up here. But it's recommended you rely on your own memory.
Rock on, homie.