Something intimidating makes you feel worried and not confident. A person can be intimidating — a tall coach, a very clever classmate, a boss who never smiles. A place or a task can be intimidating too: a huge stage, a hard exam, a long book. The word describes the thing that gives you that shrinking feeling; it does not describe the feeling itself. It is common in everyday English, a little stronger than “scary” and a little more about confidence than about danger. Though actually, people also use it with a half-smile: “That cake looks intimidating” just means it looks like a lot, not that anyone is afraid. If you say you are intimidating, you are saying other people find you hard to approach.