The Collaborative International Dictionary of English v.0.48:

Walker \Walk"er\, n.
   1. One who walks; a pedestrian.
      [1913 Webster]

   2. That with which one walks; a foot. [Obs.]
      [1913 Webster]

            Lame Mulciber, his walkers quite misgrown.
                                                  --Chapman.
      [1913 Webster]

   3. (Law) A forest officer appointed to walk over a certain
      space for inspection; a forester.
      [1913 Webster]

   4. [AS. wealcere. See Walk, v. t., 3.] A fuller of cloth.
      [Obs. or Prov. Eng. & Scot.]
      [1913 Webster]

            She cursed the weaver and the walker
            The cloth that had wrought.           --Percy's
                                                  Reliques.
      [1913 Webster]

   5. (Zool.) Any ambulatorial orthopterous insect, as a stick
      insect.
      [1913 Webster]

   6. (construction, tunneling) A shift superintendent or
      assistant superintendent who supervises several
      shifters[4] and their crews. Since these crews are usually
      separated by some distance, the walker is frequently seen
      walking between them. Also called walking boss.
      [RDH]

   7. A low frame having casters or wheels, designed to enclose
      a baby on its sides and provide support while the baby is
      learning to walk; it usually has a seat so that the baby
      can sit while not walking.

   Syn: go-cart, baby-walker.
        [PJC]

   8. A low rectangular frame of light metal about waist high,
      usually having two horizontal arms mounted on four legs
      with an open rear, designed to be carried or pushed in
      front of a person whose legs are impaired, to provide
      support while walking; it may have wheels on two of the
      four legs.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

baby-walker \baby-walker\ n.
   a framework on small wheels or casters designed to support
   small children while they are learning to walk, and usually
   having a fabric support that permits the child to sit. Called
   also walker and go-cart.

   Syn: walker, go-cart
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

Walker
    n 1: New Zealand runner who in 1975 became the first person to
         run a mile in less that 3 minutes and 50 seconds (born in
         1952) [syn: Walker, John Walker]
    2: United States writer (born in 1944) [syn: Walker, Alice
       Walker, Alice Malsenior Walker]
    3: a person who travels by foot [syn: pedestrian, walker,
       footer]
    4: a shoe designed for comfortable walking
    5: a light enclosing framework (trade name Zimmer) with rubber
       castors or wheels and handles; helps invalids or the
       handicapped or the aged to walk [syn: walker, Zimmer,
       Zimmer frame]
    6: an enclosing framework on casters or wheels; helps babies
       learn to walk [syn: walker, baby-walker, go-cart]