The Collaborative International Dictionary of English v.0.48:

emphatic \em*phat"ic\, emphatical \em*phat"ic*al\, a. [Gr. ?:
   cf. F. emphatique. See Emphasis.]
   1. Uttered with emphasis; made prominent and impressive by a
      peculiar stress of voice; laying stress; deserving of
      stress or emphasis; forcible; impressive; strong; as, to
      remonstrate in an emphatic manner; emphatic denials; an
      emphatic word; an emphatic tone; emphatic reasoning.
      [1913 Webster]

   2. Striking the sense; attracting special attention;
      impressive; forcible. "Emphatical colors." --Boyle.
      "Emphatical evils." --Bp. Reynolds.

   3. Forceful and definite in expression or action; -- of
      statements, actions, or sections of documents; as, the
      document contained a particularly emphatic guarantee of
      religious liberty.

   Syn: forceful.
        [WordNet 1.5 +PJC]

   4. Sudden and strong; -- of statements; as, an emphatic no.

   Syn: exclamatory.
        [WordNet 1.5]

   Syn: Forcible; earnest; impressive; energetic; striking;
        positive; important; special; significant.
        [1913 Webster]

WordNet (r) 3.0 (2006):

emphatic
    adj 1: spoken with emphasis; "an emphatic word" [syn:
           emphatic, emphasized, emphasised]
    2: sudden and strong; "an emphatic no" [syn: emphatic,
       exclamatory]
    3: forceful and definite in expression or action; "the document
       contained a particularly emphatic guarantee of religious
       liberty" [syn: emphatic, forceful]