1.) To slide a layer of yucky saliva on something. To taste something. 2.) A trace of something. 3.) A treasure, prize or money of some sort, as in, you caught a lick. In the world of pirates, it's a booty. When you come up on unexpected money. 4.) A lick is musical idea, but often it's incomplete. It might be a fragment of a solo or a portion of a riff. By itself, it doesn't usually become thematic---in fact, a lick that forms a theme essentially becomes a riff. A lick combines with other licks to form a complete musical idea. Because a lick isn't the main theme, it doesn't have that same association with the song, and so it's transferable: it can be used in other songs without necessarily having to allude to the original.
"Black Dog" by Led Zeppelin also uses a great lick as its main riff. They play it in different keys, but it's still recognizably the same idea. You could imagine that melodic fragment as part of a solo, but by using it as the foundation of the song, Led Zeppelin makes it a riff. I could see someone playing this at the end of their solo, and I'd think it was both clever and funny.
1.) Greek Mythology. A female monster with a talent for snatching evildoers and dropping them into the seventh ring of hell. A mutant creature with a female face, the body of a bird and sharp naughty talons for days.
2.) A shrewish woman with a bad and scolding temper.
3.) Nickname for a lesbian or muff diver.