A contraction of the words "lesbian" and "emo". I'm not sure on the origins of this word, but I heard it at school, a group of chavs called one of my friends it.
Seeing as they have only one brain cell between them, I would assume they heard it somewhere else first. It is far too clever, and my friend took it as more of an observation than an insult anyway...
Chavs: Stupid lemo.
Friend: Haha, a cross between a lemur and an emo!!
Me: It's not lemur, you dolt, lesbian + emo.
Friend: Even better!
A gay, possibly emo person that you might've used to like but is now a skank and a loser. Tends to change sexual tendencies. She is flat and has no friends. Has an obsession with bad music. Most likely vegans and virgins forever and harasses you about your lifestyle and flaws all the time.
Girl: Omg who is that new girl that transferred
Boy: Oh! she seems pretty nice.
~ 2 weeks later ~
Girl: OMG she turned out lesbian and a vegan!
Boy: UGH what a lemo
*turns pansexual a month later*