A social group based off the word lethargic, its members mostly tired slackers with low fashion sense, a tendency to play video games and magic the gathering but not at a impressive level. The construction of the word is based off of "emo" being short for "emotional".
A leth is that guy you know that plays halo with you pretty often, but never wins. A leth doesn't fall asleep in school, it just always looks like they will. A leth always was interested in playing World of Warcraft but never go around to it. A leth is somewhere between a stoner and a nerd, without the illegal or anti-social characteristics of either.
So incredibility unmotivated.
So unbelievably tired.
So over the top exhausted
So tired he can't even muster up the strength to say lethargic.
Alvin was so leth he couldn't be bothered to answer the phone next to him.
Joanne was so leth she didn't have the energy to change the channel on the remote control.
Leth is to lethargic as emo is to emotional.
Dude, I feel so leth right now. All I want to do is sit around and listen to emo music!