Let her rip is an informal phrase that means to start something or to give it your all. Some synonyms for "let her rip" include "go for it," "give it a shot," "take a chance," "take the plunge," and "take the bull by the horns." These phrases all indicate an eagerness to move forward and are often used when encouraging someone to try something new or take a risk. They are also commonly used in situations where it is necessary to act quickly and decisively. Whether you're embarking on a new adventure or tackling a challenging task, these phrases can help you summon the courage and determination to succeed.