Source : Webster's Revised Unabridged Dictionary (1913)

Adjectival \Ad`jec*ti"val\, a.
   Of or relating to the relating to the adjective; of the
   nature of an adjective; adjective. --W. Taylor (1797)

Source : WordNet®

adjectival
     adj : of or relating to or functioning as an adjective;
           "adjectival syntax"; "an adjective clause" [syn: {adjective}]