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]

The Collaborative International Dictionary of English v.0.48:

Swab \Swab\, n. [Written also swob.]
   1. A kind of mop for cleaning floors, the desks of vessels,
      etc., esp. one made of rope-yarns or threads.
      [1913 Webster]

   2. A bit of sponge, cloth, or the like, fastened to a handle,
      for cleansing the mouth of a sick person, applying
      medicaments to deep-seated parts, etc.
      [1913 Webster]

   3. (Naut.) An epaulet. [Sailor's Slang] --Marryat.
      [1913 Webster]

   4. A cod, or pod, as of beans or pease. [Obs.] --Bailey.
      [1913 Webster]

   5. A sponge, or other suitable substance, attached to a long
      rod or handle, for cleaning the bore of a firearm.
      [1913 Webster]

WordNet (r) 3.0 (2006):

swab
    n 1: implement consisting of a small piece of cotton that is
         used to apply medication or cleanse a wound or obtain a
         specimen of a secretion
    2: cleaning implement consisting of absorbent material fastened
       to a handle; for cleaning floors [syn: swab, swob, mop]
    v 1: wash with a swab or a mop; "swab the ship's decks" [syn:
         swab, swob]
    2: apply (usually a liquid) to a surface; "dab the wall with
       paint" [syn: dab, swab, swob]

The Free On-line Dictionary of Computing (19 January 2023):

swab

   /swob/ The PDP-11 swap byte instruction mnemonic, as
   immortalised in the dd option "conv=swab".

   1. To solve the NUXI problem by swapping bytes in a file.

   2.  The program in V7 Unix used to perform this action, or
   anything functionally equivalent to it.

   See also big-endian, little-endian, middle-endian,
   bytesexual.

   [Jargon File]


The Jargon File (version 4.4.7, 29 Dec 2003):

swab
 /swob/

    [From the mnemonic for the PDP-11 ‘SWAp Byte’ instruction, as
    immortalized in the dd(1) option conv=swab (see dd)]

    1. vt. To solve the NUXI problem by swapping bytes in a file

    2. n. The program in V7 Unix used to perform this action, or anything
    functionally equivalent to it. See also big-endian, little-endian, 
    middle-endian, bytesexual.