There are several synonyms for the phrase "laugh oneself silly". One alternative is "roll on the floor laughing", which highlights the intense physical reaction of the laughter. Another option is "hysterical laughter", which emphasizes the uncontrollable nature of the laughter. "Crack up" is another synonym, which refers to breaking down in uncontrollable laughter. "Bust a gut" is a more informal synonym that describes the physical strain put on the body during excessive laughter. Lastly, "roaring with laughter" is a synonym that plays off the idea of laughter being loud and boisterous. These synonyms provide colorful ways to describe the act of laughing uncontrollably.