Definition
A "back-number" refers to someone or something that is old-fashioned, outdated, or no longer relevant. It suggests something that has been superseded by newer, better things. It's similar to being a relic of the past. Imagine an old computer running outdated software π». It doesnβt quite fit in with modern standards. It can also describe a person stuck in old ways. Think of it as the opposite of being cutting-edge.