A variation of the word antonym, in a manner similar to the way synonym and synonymous are related. When several words are synonyms, they mean approximately the same thing. However, when they are synonymous, they mean exactly the same thing. Similarly, there must be a word that means exactly opposite, to pair with "antonym" which only means approximately opposite. Thus, antonymous words are words that are exact polar opposites in meaning.
To communicate an idea using the antonym of the word typically used to communicate it. In many situations, such use is more nuanced and contains deeper emotional undertones.
He told her "I hate you for doing so much good for everyone else except you"; what he meant was that he deeply loved her doing what she did despite the personal sacrifices she had to make. He antonymicated love with hate.
