To present participles which come from intransitive verbs, or are themselves employed as adjectives, to mark the absence of the activity, disposition, or condition implied by the participle;

being without physical aid; "he could not rise unaided from a sitting position"

(of the eye or ear e.g.) without the aid of an optical or acoustical device or instrument; "visible to the naked eye"; "clearly audible to the unaided ear"