"On deck" is a term used to describe the next in line or someone who is prepared and ready to go. There are several synonyms for this term that can be used interchangeably in different contexts. One such synonym is "at the ready," which means to be prepared or poised for action. Another synonym is "in waiting," which implies that the person or thing is waiting to be called upon or used. "Next up" is another alternative, particularly in sports when referring to the next player up to bat or take a turn. Other synonyms for "on deck" include "next in line" or "upcoming." These synonyms help to add variety to our language and allow us to express ourselves in different ways.