Source : Webster's Revised Unabridged Dictionary (1913)

Precautional \Pre*cau"tion*al\, a.
   Precautionary.

Source : WordNet®

precautional
     adj : taken in advance to protect against possible danger or
           failure; "gave precautionary advice"; "I would take
           precautionary steps to keep him away" [syn: {precautionary}]