un ‧ marked /ˌʌnˈmɑːkt◂ $ -ˈmɑːrkt◂/ BrE AmE adjective
[ Word Family: verb : ↑ mark ; adverb : ↑ markedly ; adjective : ↑ marked ≠ ↑ unmarked ]
something that is unmarked has no words or signs on it to show where or what it is:
an unmarked grave
an unmarked police car