The Collaborative International Dictionary of English v.0.48:

Exact \Ex*act"\, v. t. [imp. & p. p. Exacted; p. pr. & vb. n.
   Exacting.] [From L. exactus, p. p. of exigere; or fr. LL.
   exactare: cf. OF. exacter. See Exact, a.]
   To demand or require authoritatively or peremptorily, as a
   right; to enforce the payment of, or a yielding of; to compel
   to yield or to furnish; hence, to wrest, as a fee or reward
   when none is due; -- followed by from or of before the one
   subjected to exaction; as, to exact tribute, fees, obedience,
   etc., from or of some one.
   [1913 Webster]

         He said into them, Exact no more than that which is
         appointed you.                           --Luke. iii.
                                                  13.
   [1913 Webster]

         Years of servise past
         From grateful souls exact reward at last --Dryden.
   [1913 Webster]

         My designs
         Exact me in another place.               --Massinger.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Exacting \Ex*act"ing\, a.
   Oppressive or unreasonably severe in making demands or
   requiring the exact fulfillment of obligations; harsh;
   severe. "A temper so exacting." --T. Arnold --
   Ex*act"ing*ly, adv. -- Ex*act"ing*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

exacting
    adj 1: having complicated nutritional requirements; especially
           growing only in special artificial cultures; "fastidious
           microorganisms"; "certain highly specialized xerophytes
           are extremely exacting in their requirements" [syn:
           fastidious, exacting] [ant: unfastidious]
    2: severe and unremitting in making demands; "an exacting
       instructor"; "a stern disciplinarian"; "strict standards"
       [syn: stern, strict, exacting]
    3: requiring precise accuracy; "an exacting job"; "became more
       exigent over his pronunciation" [syn: exigent, exacting]