"A fast worker" is a phrase used to describe an individual who is efficient and quick in completing tasks. However, there are several synonyms for this phrase that can be used to add variety and depth to our expression. Some other terms that can be used instead of "a fast worker" include "a quick achiever," "an adept doer," "a swift performer," "a speedy executor," "a speedy implementer," "a rapid operator," "a lightning-quick worker," and "a prompt achiever." Using these synonyms can help in diversifying our language and make our writing more interesting and appealing.