Source : Webster's Revised Unabridged Dictionary (1913)

Terrific \Ter*rif"ic\, a. [L. terrificus; fr. terrere to
   frighten + facere to make. See {Terror}, and {Fact}.]
   Causing terror; adapted to excite great fear or dread;
   terrible; as, a terrific form; a terrific sight.

Source : WordNet®

terrific
     adj 1: very great or intense; "a terrific noise"; "a terrific
            thunderstorm storm"; "fought a terrific battle"
     2: extraordinarily good; used especially as intensifiers; "a
        fantastic trip to the Orient"; "the film was fantastic!";
        "a howling success"; "a marvelous collection of rare
        books"; "had a rattling conversation about politics"; "a
        tremendous achievement" [syn: {fantastic}, {howling(a)}, {marvelous},
         {marvellous}, {rattling(a)}, {tremendous}, {wonderful}, {wondrous}]
     3: causing extreme terror; "a terrifying wail" [syn: {terrifying}]