Rapidly; with speed; fast.
"The cheetah spotted its prey and quickly closed the distance in a blur of motion."
In plain English: Quickly means doing something very fast with little time wasted.
"She quickly finished her homework before dinner was served."
Usage: Use quickly to describe how an action happens in a short amount of time, such as running or eating. It functions as an adverb modifying verbs and should not be confused with the adjective quick when describing nouns like "a quick meal."
The word "quickly" comes from Middle English and Old English, where it originally meant "with a living or active quality." It is formed by adding the suffix "-ly" to the root word "quick."