The phrase "broad side foremost" means to hit or face something with the broad side of an object. Synonyms for this term can vary based on the context in which it is used. In a nautical sense, the term could refer to "beam-on," or the angle at which a ship is facing sideways. In a confrontation, "full frontal" or "face-on" could be used to indicate an attack or defense from the front. In a physical confrontation, "bull rush" or "tackle head-on" could describe charging at someone or something with force. Ultimately, the synonym depends on the specific situation and the perspective of the speaker.