The Collaborative International Dictionary of English v.0.48:

Tire \Tire\, v. i. [imp. & p. p. Tired; p. pr. & vb. n.
   Tiring.] [OE. teorien to become weary, to fail, AS. teorian
   to be tired, be weary, to tire, exhaust; perhaps akin to E.
   tear to rend, the intermediate sense being, perhaps, to wear
   out; or cf. E. tarry.]
   To become weary; to be fatigued; to have the strength fail;
   to have the patience exhausted; as, a feeble person soon
   tires.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tiring
    adj 1: producing exhaustion; "an exhausting march"; "the visit
           was especially wearing" [syn: exhausting, tiring,
           wearing, wearying]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "tiring":
   boresome, boring, draining, drudging, exhausting, fatiguesome,
   fatiguing, grueling, irksome, killing, punishing, straining,
   stressful, stupefyingly boring, stuporific, tedious, tiresome,
   toilsome, trying, weariful, wearing, wearisome, wearying, yawny