"March the cannon's mouth" is a phrase that refers to the act of facing danger or taking a risk. Synonyms for this phrase may include "take the plunge," "brave the storm," "dare to venture," or "step into the fray." Other synonyms for "marching the cannon's mouth" may include "leap of faith," "bold move," "courageous decision," or "risk it all." These phrases all denote a sense of bravery, determination, and willingness to face obstacles or challenges head-on. Whatever phrase is used, "marching the cannon's mouth" demonstrates a willingness to take action despite the potential hazards and the uncertain nature of the outcome.