The crossword solution for the term OPP. OF SYN. is ANT, which is a three-letter word. Ants are small insects that live in colonies and are known for their hard work and organization. They are often used as a metaphor for people who work together in a cooperative manner. Ants are also known for their ability to adapt to their environment and survive in harsh conditions. In terms of synonyms, an ANT is the opposite of a synonym, which is a word or phrase that has the same or nearly the same meaning as another word or phrase.