The Collaborative International Dictionary of English v.0.48:

Requisite \Req"ui*site\ (r?k"w?-z?t), n.
   That which is required, or is necessary; something
   indispensable.
   [1913 Webster]

         God, on his part, has declared the requisites on ours;
         what we must do to obtain blessings, is the great
         business of us all to know.              --Wake.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Requisite \Req"ui*site\, a. [L. requisitus, p. p. requirere;
   pref. re- re- + quaerere to ask. See Require.]
   Required by the nature of things, or by circumstances; so
   needful that it can not be dispensed with; necessary;
   indispensable.
   [1913 Webster]

         All truth requisite for men to know.     --Milton.
   [1913 Webster]

   Syn: Necessary; needful; indispensable; essential.
        [1913 Webster] -- Req"ui*site*ly, adv. --
        Req"ui*site*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

requisite
    adj 1: necessary for relief or supply; "provided them with all
           things needful" [syn: needed, needful, required,
           requisite]
    n 1: anything indispensable; "food and shelter are necessities
         of life"; "the essentials of the good life"; "allow farmers
         to buy their requirements under favorable conditions"; "a
         place where the requisites of water fuel and fodder can be
         obtained" [syn: necessity, essential, requirement,
         requisite, necessary] [ant: inessential,
         nonessential]