the GNU version of the Collaborative International Dictionary of English
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
The Century Dictionary and Cyclopedia
Not liable; not subject; not exposed.
Not obnoxious; not offensive or hateful.
Word Usage
"Perhaps advertising actually can be informative, unobnoxious, and useful."