The crossword solution for the term antonym of post is 'pre'. Pre is a prefix that means before or in front of. It is often used to describe something that happens before something else, such as in the phrase 'pre-existing condition'. It can also be used to describe something that is done before something else, such as in the phrase 'pre-planning'. Pre is also used to describe something that is done in advance, such as in the phrase 'pre-payment'.