The characteristic vocalization of a male lion is called a roar.
A lion’s roar is a powerful long-distance signal used in territorial and social communication. Adult males are especially well known for roaring, although females can roar too. Roaring may help advertise the presence of a pride, maintain contact and warn rival lions away.
The sound is enabled in part by the lion’s specialized larynx and vocal folds. Lions can produce deep, resonant calls that travel across open habitats, particularly at night when sound conditions may be favorable. A roar is not simply an expression of anger; its meaning depends on context and the surrounding social situation.
Lions also use other sounds, including grunts, snarls, growls, moans and contact calls. “Roar” is therefore the canonical name for the famous long-distance call, not a label for every loud noise a lion makes.