Amused oneself is a phrase used to define engaging in activities that bring entertainment, joy, or pleasure. However, antonyms for this word could denote the opposite emotions or actions. The antonym for the word "amused" is "bored" or "uninterested," implying the urge to find something entertaining. On the other hand, synonyms for the word "self" are societal or the general population, connoting engaging in activities both pleasing and helpful for others. Doing more things that are beneficial for others may lead to emotions like fulfillment and happiness, which are antonyms of boredom and uninterest. Therefore, the antonyms for "amused oneself" could be lonely or bored, depending on the context.