The Collaborative International Dictionary of English v.0.48:

titanic \ti*tan"ic\ (t[-i]*t[a^]n"[i^]k), a.
   Of or relating to Titans, or fabled giants of ancient
   mythology; hence, enormous in size or strength; as, Titanic
   structures.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Titanic \Ti*tan"ic\, prop. n.
   The name of a large ocean liner which hit an iceberg and sank
   on its maiden voyage from England to New York in 1912, with
   the loss of hundreds of lives. Also, the name of several
   movies made about the incident.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

titanic \ti*tan"ic\ (t[-i]*t[a^]n"[i^]k), a. [Cf. F. titanique.]
   (Chem.)
   Of or pertaining to titanium; derived from, or containing,
   titanium; specifically, designating those compounds of
   titanium in which it has a higher valence as contrasted with
   the titanous compounds.
   [1913 Webster]

   titanic acid (Chem.), a white amorphous powder, Ti(OH)4,
      obtained by decomposing certain titanates; -- called also
      normal titanic acid. By extension, any one of a series
      of derived acids, called also metatitanic acid,
      polytitanic acid, etc.

   Titanic iron ore. (Min.) See Menaccanite.
      [1913 Webster]

WordNet (r) 3.0 (2006):

titanic
    adj 1: of great force or power

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "titanic":
   Atlantean, Brobdingnagian, Cyclopean, Gargantuan, Herculean,
   Homeric, abysmal, amplitudinous, astronomic, astronomical, awesome,
   boundless, bulky, colossal, cosmic, cyclopean, elephantine,
   enormous, epic, extensive, galactic, gargantuan, giant, giantlike,
   gigantic, heroic, huge, immeasurable, immense, infinite, jumbo,
   king-size, large, mammoth, massive, massy, mighty, monster,
   monstrous, monumental, mountainous, outsize, overgrown, prodigious,
   profound, sizable, spacious, stupendous, towering, tremendous,
   vast, voluminous, weighty