Source : Webster's Revised Unabridged Dictionary (1913)

Precaution \Pre*cau"tion\, n. [F. pr['e]cation, L. praecautio,
   fr. praecavere, praecautum, to guard against beforehand; prae
   before + cavere be on one's guard. See {Pre-}, and
   {Caution}.]
   1. Previous caution or care; caution previously employed to
      prevent mischief or secure good; as, his life was saved by
      precaution.

            They [ancient philosophers] treasured up their
            supposed discoveries with miserable precaution. --J.
                                                  H. Newman.

   2. A measure taken beforehand to ward off evil or secure good
      or success; a precautionary act; as, to take precautions
      against accident.

Precaution \Pre*cau"tion\, v. t. [Cf. F. pr['e]cautionner.]
   1. To warn or caution beforehand. --Locke.

Source : WordNet®

precaution
     n 1: a precautionary measure warding off impending danger or
          damage or injury etc.; "he put an ice pack on the injury
          as a precaution"; "an insurance policy is a good
          safeguard"; "we let our guard down" [syn: {safeguard}, {guard}]
     2: the trait of practicing caution in advance
     3: judiciousness in avoiding harm or danger; "he exercised
        caution in opening the door"; "he handled the vase with
        care" [syn: {caution}, {care}, {forethought}]