Snarl



A snarl is a facial expression, where the upper lip is raised, and the nostrils widen, generally indicating hate, anger or pain. In addition to humans, other mammals including monkeys and dogs snarl, often to warn others of their potential bite. In humans, snarling uses the levator labii superioris alaeque nasi muscle.

Snarling is often accompanied by threatening vocalizations. As a result, by misunderstanding phrases such as "the dog was growling and snarling", "snarling" is often used to mean the threatening noise, sometimes as an onomatopoeia, as in the 'snarl' of a chainsaw).

Reference
Brontolìo