To drool means to let saliva dribble out of your mouth without meaning to. Babies drool constantly because they haven't yet learned to control their mouth muscles. Dogs drool when they see food or get excited. You might drool a little while sleeping, leaving a damp spot on your pillow.

People sometimes drool when they're extremely tired, sick, or when their mouth is numb from a dentist's visit.

Drool can also describe what happens when you see something you desperately want. If you drool over the dessert display at a bakery, you're staring at those pastries with intense longing. When your friend shows you their new gaming system, you might say, “I was totally drooling!” You're not actually dripping saliva, but you want that thing so badly you can almost taste it. This figurative use captures that same uncontrolled, automatic reaction: just as your mouth waters involuntarily at the smell of pizza, your desire takes over when you see something amazing.