1. [adj]  not objectionable; "the ends are unobjectionable; it's the means that one can't accept"
2. [adj]  (of behavior or especially language) free from objectionable elements; fit for all observers; "good clean fun"; "a clean joke"
3. [adj]  not causing disapproval; "it was an innocuous remark"; "confined himself to innocuous generalities"; "unobjectionable behavior"

UNOBJECTIONABLE is a 15 letter word that starts with U.