1. Literally, to lick one's lips in anticipation of eating something delicious. This nutritious recipe is sure to have your kids smacking their lips!

2. By extension, to eagerly anticipate something with great pleasure. Property developers have been smacking their lips at the thoughts of getting their hands on such prime real estate.

3. To make unintentional smacking noises with one's mouth, especially when speaking. Try not to smack your lips when you lean into the mic, it's really loud in the headphones.