For me, this most often comes up when acting as a reference for someone. The hiring person will ask me stuff, and often a 'senior' label question will come up. Almost invariably the person I'm acting as a reference for is beyond 'junior' connotations, and I think have to ask what the hiring person mean by 'senior'. Getting their definition helps me answer most effectively.

"Yeah, AB is pretty close to what you class as 'senior'. He's going to work well in a larger group with defined roles and a set schedule, which it sounds like you have."

"Well.. SJ is not 'junior' any more, but does need to have someone more senior to help mentor/check in on more advanced topics. If you don't have that - if this is a 'lone wolf' role, they may struggle some".