IPA: /ʌnˈmɑːrkt/
KK: /ʌnˈmɑrkt/
Something that does not have any identifying marks or labels on it.
The unmarked package arrived at my door without any indication of its contents.
Unmarked → It is formed from "un-" (meaning not) and "marked" (from Old English "mearcian", meaning to mark or designate). The word "unmarked" means not marked or not designated in any way.
Think of 'not' ('un-') having a 'mark' ('marked') — so unmarked means something that does not have a mark.