There are several synonyms for the phrase "active use," which generally refers to the actual operation or utilization of something. These synonyms include "actual utilization," "direct application," "real-time use," "practical use," "hands-on use," "operational usage," "functional implementation," and "live practice." All of these phrases convey the idea that the object or concept in question is being actively engaged with in a practical, tangible way. Whether it's a tool being used in a workshop or a language being spoken in a conversation, active use implies that something is being put into action and generating results.