Source : Webster's Revised Unabridged Dictionary (1913)

Swop \Swop\, v. & n.
   Same as {Swap}. --Dryden.

Source : WordNet®

swop
     n : an equal exchange; "we had no money so we had to live by
         barter" [syn: {barter}, {swap}, {trade}]
     v : exchange or give (something) in exchange for [syn: {trade},
         {swap}, {switch}]