Example:
When it saw Harold preparing the barbecue, and smelled the meat which had started to cook, the dog began to drool. 
sputnik
Photo license:
CC: Attribution, Commercial Use
Regionalism:
Neutral
Regional variant:
Neutral
Full Expression:
The “ool” Sound ( /u:/ ) : drool
when saliva spills out of a person's or animal's mouth involuntarily