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]

Moby Thesaurus II by Grady Ward, 1.0:

152 Moby Thesaurus words for "exacting":
   Herculean, Spartan, Spartanic, abstruse, accurate, arduous,
   arousing, astringent, attentive, austere, authoritarian, brutal,
   burdensome, censorious, choicy, choosy, clamant, clamorous, close,
   complex, conscientious, correct, critical, crying, cutthroat,
   delicate, demanding, detailed, difficile, difficult,
   discriminating, discriminative, dour, draining, educible, eductive,
   elicitory, eradicative, evocative, exact, exactive, excessive,
   exigent, exorbitant, exquisite, extortionary, extortionate,
   extortive, extractive, extravagant, fancy, fastidious, fine,
   finical, finicking, finicky, formidable, fussy, gouging, grasping,
   grievous, grim, grossly overpriced, hairy, hard, hard-earned,
   hard-fought, harsh, hypercritical, immoderate, imperative,
   importunate, inflationary, inordinate, insistent, instant,
   intricate, jawbreaking, knotted, knotty, laborious, loud, mean,
   meticulous, minute, narrow, nice, no picnic, not easy, operose,
   oppressive, out of bounds, out of sight, outrageous, overpriced,
   particular, perfectionistic, persistent, pertinacious, picky,
   precise, precisianistic, precisionistic, preposterous, pressing,
   priggish, prohibitive, prudish, punctilious, punctual, puristic,
   puritanic, refined, religious, rigid, rigorous, rough, rugged,
   scrupulous, scrutinizing, selective, sensitive, set with thorns,
   severe, skyrocketing, spiny, spiraling, steep, stern, strenuous,
   strict, stringent, subtle, taxing, thorny, ticklish, toilsome,
   tough, tricky, trying, tyrannical, unconscionable, undue,
   unreasonable, unsparing, unwarranted, uphill, uprooting, urgent,
   usurious, weighty, wicked