Linguistics. characterized by the absence of a distinctive phonological feature, as (p), which, in contrast to (b), lacks the distinctive feature of voicing. characterized by the absence of a grammatical marker, as the singular in English in contrast to the plural, which is typically marked by an -s ending. neutral with regard to an element of meaning specified by a semantically related item. occurring more typically than an alternative form. Compare marked (def 4).
not carrying a mark or marks: an unmarked police car