Source : Webster's Revised Unabridged Dictionary (1913)

Crucial \Cru"cial\ (kr?"shal), a. [F. crucial, fr. L. crux,
   crucis, cross, torture. See {Cross}.]
   1. Having the form of a cross; appertaining to a cross;
      cruciform; intersecting; as, crucial ligaments; a crucial
      incision.

   2. Severe; trying or searching, as if bringing to the cross;
      decisive; as, a crucial test.

Source : WordNet®

crucial
     adj 1: of extreme importance; vital to the resolution of a crisis;
            "a crucial moment in his career"; "a crucial
            election"; "a crucial issue for women" [syn: {important}]
            [ant: {noncrucial}]
     2: having crucial relevance; "crucial to the case"; "relevant
        testimony" [syn: {relevant}]
     3: of the greatest importance; "the all-important subject of
        disarmament"; "crucial information"; "in chess cool nerves
        are of the essence" [syn: {all-important(a)}, {all
        important(p)}, {essential}, {of the essence(p)}]
     4: having the power or quality of deciding; "the crucial
        experiment"; "cast the deciding vote"; "the determinative
        (or determinant) battle" [syn: {deciding(a)}, {determinant},
         {determinative}, {determining(a)}]