Source : Webster's Revised Unabridged Dictionary (1913)

Apparent \Ap*par"ent\, a. [F. apparent, L. apparens, -entis, p.
   pr. of apparere. See {Appear}.]
   1. Capable of being seen, or easily seen; open to view;
      visible to the eye; within sight or view.

            The moon . . . apparent queen.        --Milton.

   2. Clear or manifest to the understanding; plain; evident;
      obvious; known; palpable; indubitable.

            It is apparent foul play.             --Shak.

   3. Appearing to the eye or mind (distinguished from, but not
      necessarily opposed to, true or real); seeming; as the
      apparent motion or diameter of the sun.

            To live on terms of civility, and even of apparent
            friendship.                           --Macaulay.

            What Berkeley calls visible magnitude was by
            astronomers called apparent magnitude. --Reid.

   {Apparent horizon}, the circle which in a level plain bounds
      our view, and is formed by the apparent meeting of the
      earth and heavens, as distinguished from the rational
      horizon.

   {Apparent time}. See {Time}.

   {Heir apparent} (Law), one whose to an estate is indefeasible
      if he survives the ancestor; -- in distinction from
      presumptive heir. See {Presumptive}.

   Syn: Visible; distinct; plain; obvious; clear; certain;
        evident; manifest; indubitable; notorious.

Heir \Heir\, n. [OE. heir, eir, hair, OF. heir, eir, F. hoir, L.
   heres; of uncertain origin. Cf. {Hereditary}, {Heritage}.]
   1. One who inherits, or is entitled to succeed to the
      possession of, any property after the death of its owner;
      one on whom the law bestows the title or property of
      another at the death of the latter.

            I am my father's heir and only son.   --Shak.

   2. One who receives any endowment from an ancestor or
      relation; as, the heir of one's reputation or virtues.

            And I his heir in misery alone.       --Pope.

   {Heir apparent}. (Law.) See under {Apparent}.

   {Heir at law}, one who, after his ancector's death, has a
      right to inherit all his intestate estate. --Wharton (Law
      Dict.).

   {Heir presumptive}, one who, if the ancestor should die
      immediately, would be his heir, but whose right to the
      inheritance may be defeated by the birth of a nearer
      relative, or by some other contingency.

Source : WordNet®

heir apparent
     n : an heir whose right to an inheritance cannot be defeated if
         that person outlives the ancestor [ant: {heir presumptive}]