* ばか (baka) - This is the most common word for "dumb" in Japanese. It can be used to refer to someone who is stupid or foolish, or it can be used as an insult.
* あほう (ahou) - This is another word for "dumb" that is similar to ばか. It is also used to refer to someone who is stupid or foolish, or it can be used as an insult.
* まぬけ (manuke) - This word means "fool" or "idiot." It is usually used in a humorous way, but it can also be used as an insult.
* おろか (oroka) - This is a more formal word for "dumb" that is used in writing. It is often used to describe someone who is ignorant or uninformed.