Five words cover a lot of territory. "Wacky" is really a slang word, in my opinion, close in meaning to "zany". We might use these words to describe a person's behavior. "Eccentric" also describes a person's behavior, but is is an academic word with Greek roots. (The joke is that a poor person might be "crazy", but a rich person is only "eccentric".) "Ridiculous" has Latin roots, but it is used more generally to describe things or conditions. "Crazy" is not an academic word; it is used commonly to relate to all kinds of behaviors and situations. I hope this helps.