The phrase "march the cannon mouth" is a figurative expression that means to go forward with determination, tenacity, and confidence. There are several other words and phrases that could be used as synonyms for this expression, including "forge ahead," "press on," "persevere," "keep moving forward," "push through," and "never give up." All of these expressions connote a sense of strong motivation and an unwavering resolve to achieve one's goals, despite any challenges or setbacks that may arise. No matter what words are used, the underlying message is clear: Keep pushing forward, no matter what obstacles may stand in your way.