A severe fear of heights is known as what?

A severe fear of heights is referred to as acrophobia. This specific phobia is characterized by intense anxiety or fear when someone is in high places or even when thinking about heights. Symptoms can include feelings of panic, dizziness, or a sense of losing control.

In the context of the other options, agoraphobia refers to the fear of situations where escape may be difficult, leading to avoidance behavior particularly in crowded places. Aerophobia is the fear of flying, which is distinct from the fear of heights in general. Ailurophobia is the fear of cats, showcasing how specific phobias can target various animals or situations. Each of these terms describes different types of anxieties, but acrophobia specifically addresses the fear associated with heights, making it the correct answer.