Literally - Image #864,012

You are not supposed to use the word you are defining within the definition of the word. If someone does not know the meaning of the word the using the word to define the word does not help them understand it.

Also, a word should not be an antonym of itself. When a word as two meanings that are the opposite of each other that makes it impossible to interpret the meaning when someone is using the word.

This is the reason why people make a big deal out of misusing the word.