unmarked
adj.having no visible signs, labels, or decorations. You use this to describe something that is plain or does not show any clear information.
adj.lacking identifying marks, labels, or distinguishing features. In linguistics, refers to a standard form that is not modified by extra sounds or endings.
“The police drove an unmarked car to stay hidden.”
“The delivery arrived in an unmarked box, so we had no idea what was inside until we opened it.”
“In many languages, the singular form of a noun is unmarked, while the plural requires an additional suffix to indicate the change in number.”
Often used to describe vehicles, graves, or packages that lack identification.
From un- + marked.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.