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]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "emphatic":
   absolute, accented, accentuated, affirmative, affirmatory,
   aggressive, ardent, assertative, assertional, assertive, burning,
   categorical, certain, decided, declarative, declaratory, definite,
   definitive, determined, direct, distinct, dogged, dogmatic,
   earnest, emphasized, energetic, enthusiastic, exciting, explicit,
   express, fervent, fiery, firm, forceful, forcible, glowing,
   impassioned, in red letters, incisive, insistent, intense,
   italicized, marked, passionate, peremptory, pointed, positive,
   predicational, predicative, pronounced, provoking, punctuated,
   resolute, resounding, specific, starred, stimulating, stirring,
   stressed, strong, sure, unambiguous, uncompromising, underlined,
   underscored, unequivocal, unmistakable, urgent, vehement, vigorous,
   warm