Something premeditated is planned in advanced and has a purpose behind it. In other words, it's no accident. A premeditated crime involves careful planning and research before it happens.
Premeditated comes from a combination of two Latin words: pre, meaning "before," and meditat, meaning “to ponder.” If you ponder — or think about — something before you act, that makes it premeditated. If you watch a lot of TV crime dramas, you may be familiar with the term "premeditated murder." This means that the murderer didn't just lose his temper and kill someone in the moment — instead, he went after a specific person on purpose.