The Collaborative International Dictionary of English v.0.48:

Swab \Swab\, v. t. [imp. & p. p. Swabbed; p. pr. & vb. n.
   Swabbing.] [See Swabber, n.]
   To clean with a mop or swab; to wipe when very wet, as after
   washing; as, to swab the desk of a ship. [Spelt also swob.]
   [1913 Webster]