Going flatout means going at maximum speed or doing something with maximum effort and intensity. Some synonyms for this phrase include going all out, pushing oneself to the limit, working tirelessly, exerting oneself to the fullest, and putting one's nose to the grindstone. Other similar phrases include hitting the gas pedal, burning the midnight oil, working like a dog, and giving it one's all. Whatever phrase or synonym is used, the ultimate goal is to achieve a task with the greatest amount of effort and dedication, leaving nothing behind and doing the best possible job.