The Collaborative International Dictionary of English v.0.48:

Irk \Irk\ ([~e]rk), v. t. [OE. irken to tire, become tired; cf.
   Sw. yrka to urge, enforce, press, or G. ekel disgust, MHG.
   erklich disgusting; perh. akin to L. urgere to urge, E.
   urge.]
   To weary; to give pain; to annoy.
   [1913 Webster]

         To see this sight, it irks my very soul. --Shak.
   [1913 Webster]

         It irketh him to be here.                --M. Arnold.
   [1913 Webster]

WordNet (r) 3.0 (2006):

irk
    v 1: irritate or vex; "It galls me that we lost the suit" [syn:
         gall, irk]