The Collaborative International Dictionary of English v.0.48:

Irp \Irp\, Irpe \Irpe\ ([~e]rp), n. [Etymol. uncertain.]
   A fantastic grimace or contortion of the body. [Obs.]
   [1913 Webster]

         Smirks and irps and all affected humors. --B. Jonson.
   [1913 Webster]