In double time refers to performing a certain activity or action at twice the regular speed. Synonyms for this phrase include "at a fast clip," "at breakneck speed," "expeditiously," "swiftly," "with haste," "in a hurry," "speedily," "promptly," "quickly," "rapidly," "briskly," and "hurriedly." These synonyms all suggest a sense of urgency and efficiency, indicating that something needs to be done quickly and efficiently. In double time is a military term for marching twice as fast, so these synonyms are useful for describing not only physical activities but also any task that requires urgency and quickness.