A lick, in the context of music, is "a stock pattern or phrase". They are different from riffs in that they tend to be single note melodies as opposed to chord progressions. Musicians usually play licks during a solo, and they are generally seen in Jazz and Rock and Roll. There is, however, one lick that is far more famous and widespread than all the others; it is known as The Lick.

The Lick is a series of notes that turns up in a ridiculously large number of songs. Don't believe me? Check out The Lick and The Lick II. It is so well known that it even has its own Facebook page.

In the key of A minor, for example, the notes for The Lick would be:

Treble Clef
|---------|----------------------,------------------------|-----------------|-||
| | , |\ | | ||
|---------|----------,-----|\---●'------,-----------------|-----------------|-||
| 4 | , |\ ●' | , | | ||
|---------|----|\---●'-----------------●'------,------|\--|-----------------|-||
| 4 | ●' |\ ●' | ○ | ||
|------,--|-----------------------------------●'------\---|---/-------------|-||
| |\ | '--|--' | ||
|-----●'--|-----------------------------------------------|-----------------|-||

 


Try and see if you can find The Lick in your own music collections.


Sources:
http://en.m.wikipedia.org/wiki/Lick_(music)
http://www.jazzguitar.be/blog/the-lick/