So like the title asks, I'm wondering if it's legitimate to say 「意味する」 to mean "to mean". I know 意味 is meaning, and I was wondering what the verb version of 'to mean' would be. An example sentence would be "I didn't mean that." How would I translate that into Japanese? Or is there a different verb I would use?
意味する is a stiff transitive verb which means "(for a word/phrase/fact) to mean". Note that the subject cannot be a person or person pronoun like 私. The subject of 意味する is usually a (difficult) word/phrase, sometimes a certain fact or a phenomenon.
A grand-grandfather means the father of a grandparent.
What is the word that means the father of a grandparent?
The fact that he came meant the mission was successful.
"I didn't mean it" usually translates to そういう意味ではありません, そういうつもりではありません, そうじゃない, etc. If you want to say "(Sorry,) I didn't mean it" after you did something wrong, consider 悪気はなかったんです or そういうつもりではなかったんです. "She means ～" is 彼女が言いたいのは～です, etc.