The Collaborative International Dictionary of English v.0.48:

Operose \Op"er*ose`\ a. [L. operosus, fr. opera pains, labor,
   opus, operis, work, labor.]
   Wrought with labor; requiring labor; hence, tedious;
   wearisome. "Operose proceeding." --Burke. "A very operose
   calculation." --De Quincey. -- Op"er*ose`ly, adv. --
   Op"er*ose`ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

operose
    adj 1: characterized by effort to the point of exhaustion;
           especially physical effort; "worked their arduous way up
           the mining valley"; "a grueling campaign"; "hard labor";
           "heavy work"; "heavy going"; "spent many laborious hours
           on the project"; "set a punishing pace" [syn: arduous,
           backbreaking, grueling, gruelling, hard, heavy,
           laborious, operose, punishing, toilsome]

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "operose":
   Herculean, abstruse, arduous, assiduous, backbreaking, brutal,
   burdensome, complex, critical, crushing, delicate, demanding,
   difficile, difficult, diligent, effortful, elaborate, exacting,
   forced, formidable, grueling, hairy, hard, hard-earned,
   hard-fought, heavy, hefty, industrious, intricate, jawbreaking,
   killing, knotted, knotty, labored, laborious, mean, no picnic,
   not easy, onerous, oppressive, painful, painstaking, punishing,
   rigorous, rough, rugged, sedulous, set with thorns, severe, spiny,
   steep, strained, strenuous, thorny, thorough, thoroughgoing,
   ticklish, toilsome, tough, tricky, troublesome, uphill, wearisome,
   wicked