Source : Webster's Revised Unabridged Dictionary (1913)

Ethic \Eth"ic\, Ethical \Eth"ic*al\, a. [L. ethicus, Gr. ?, fr.
   ? custom, usage, character, dwelling; akin to ? custom, Goth.
   sidus, G. sitte, Skr. svadh?, prob. orig., one's own doing;
   sva self + dh? to set: cf. F. ['e]thique. See {So}, {Do}.]
   Of, or belonging to, morals; treating of the moral feelings
   or duties; containing percepts of morality; moral; as, ethic
   discourses or epistles; an ethical system; ethical
   philosophy.

         The ethical meaning of the miracles.     --Trench.

   {Ethical dative} (Gram.), a use of the dative of a pronoun to
      signify that the person or thing spoken of is regarded
      with interest by some one; as, Quid mihi Celsus agit? How
      does my friend Celsus do?

Source : WordNet®

ethical
     adj 1: of or relating to the philosophical study of ethics;
            "ethical codes"; "ethical theories"
     2: conforming to accepted standards of social or professional
        behavior; "an ethical lawyer"; "ethical medical practice";
        "an ethical problem"; "had no ethical objection to
        drinking"; "Ours is a world of nuclear giants and ethical
        infants"- Omar N. Bradley [ant: {unethical}]
     3: adhering to ethical and moral principles; "it seems ethical
        and right"; "followed the only honorable course of
        action"; "had the moral courage to stand alone" [syn: {honorable},
         {honourable}, {moral}]