Double-quick time is a phrase used to describe something that is done very quickly or at a fast pace. However, there are various synonyms for double-quick time that can be used to add variety to your language. Some of the synonyms include briskly, rapidly, swiftly, expeditiously, hastenly, nimbly, agilely, and quickly. Each of these synonyms can be used to convey that something is happening quickly, without having to resort to the overused phrase "double-quick time." So, go ahead and use these synonyms to add some flair to your language and make your writing or speech more interesting and engaging.