There are numerous synonyms for the phrase "get on with it", which is often used to encourage someone to take action or move forward with a task. Some of the most common synonyms include "proceed", "forge ahead", "carry on", "continue", and "advance". Other similar phrases that convey a sense of urgency or determination include "get cracking", "get moving", "get busy", and "get going". The important thing to remember is that many of these synonyms have slightly different connotations, so it's important to choose the one that best fits the situation and the tone you want to convey.