nondescript
So plain and ordinary that it is easy to forget.
Nondescript means so ordinary and unremarkable that it's hard to describe or remember. When something is nondescript, it has no interesting or distinctive features that make it stand out.
A nondescript building might be plain gray concrete with no decoration or character, the kind of building you could walk past every day and never really notice. A nondescript car could be an average-sized sedan in beige or gray, nothing flashy or memorable about it. When a witness tells police the suspect wore “nondescript clothing,” they mean ordinary clothes that could belong to almost anyone: plain jeans, a basic T-shirt, nothing special.
Writers sometimes use nondescript intentionally. A spy story might describe an agent as deliberately nondescript, dressed to blend into a crowd without attracting attention. In daily life, though, calling something nondescript usually means it lacks personality or charm. A nondescript restaurant might serve okay food but have nothing that makes you want to return. A nondescript room might be clean and functional but completely forgettable, with blank walls and generic furniture that could fit almost anywhere.