"Get the horn" is a slang term that means to become sexually aroused. In order to find antonyms for this phrase, we need to look for terms that represent the opposite of sexual arousal. These could include words like disinterested, indifferent, uninterested, asexual, frigid, impotent, or unresponsive. Additionally, terms that represent negative feelings or emotions towards sexuality, such as repulsion or revulsion, could also be considered antonyms. It's important to note that antonyms can vary depending on context and personal interpretation, so what may be an antonym for one person may not be for another.