One of two things.
L standing for Lose. So when your playing a game or anything really, it's possible to take a L, once again, standing for lose.
And L, as in the character from Death Note which has black hair and is majorly intelligent regarding the Kira case, of course, almost solving it.
Tim: "Darn! I can't believe I lost that game!"
Jake: "Heh, you just took a L, didn't you? "
is for the way you look at me
person 1: O is for the only one i see
person 2: V is very very extraordinary
An amazing human being who is very kind and is always there when you need them. Having an L as your bestie makes your world so much brighter, and include so many more rainbows.
Person 1: Do yk L
Person 2: Oh ya, L is amazing :)