If something is imitative, it copies a person, a style, or a sound — and in essays the word often carries a little sting. An imitative singer copies another singer's tricks instead of finding a voice of their own; an imitative film follows a fashion rather than making something new. Teachers and critics use it when they mean 'this is not original; it has no ideas of its own'. It can be kinder, though actually. A child's speech is imitative because children learn by copying, and that is how learning starts. Some words are called imitative when they copy a sound (buzz, splash). The sense you will meet in school writing is usually the unkind one: copying because you have nothing of your own to say.