To terrorize people is to frighten them again and again, on purpose, usually by threatening to hurt them — and usually so that they will do what you want or stay too afraid to act. Two things make it different from simply 'frighten'. It is deliberate, and it goes on: a gang terrorizes a neighbourhood over months, a bully terrorizes a younger student all term, armed groups terrorize a village. A single loud noise scares you; it does not terrorize you. The word is strong and serious, common in news reports and in talk about crime, war, and abuse. English speakers also use it lightly, as a joke, for something small and repeated: 'my cat terrorizes the dog', 'the two-year-old terrorizes the whole house'. Everyone hears that as playful, because the real word is so heavy that shrinking it is obviously a joke. Spelling: '-ize' is standard in American English and also fine in British English, but many British writers prefer 'terrorise'; both are correct, so pick one and stay with it.