The Collaborative International Dictionary of English v.0.48:

Perambulator \Per*am"bu*la`tor\, n.
   1. One who perambulates.
      [1913 Webster]

   2. A surveyor's instrument for measuring distances. It
      consists of a wheel arranged to roll along over the
      ground, with an apparatus of clockwork, and a dial plate
      upon which the distance traveled is shown by an index. See
      Odometer.
      [1913 Webster]

   3. A low carriage for a child, propelled by pushing; a baby
      carriage; -- called also pram, in Britain.
      [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Ambulator \Am"bu*la`tor\, n.
   1. One who walks about; a walker.
      [1913 Webster]

   2. (Zool.)
      (a) A beetle of the genus Lamia.
      (b) A genus of birds, or one of this genus.
          [1913 Webster]

   3. An instrument for measuring distances; -- called also
      perambulator. --Knight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

perambulator
    n 1: a small vehicle with four wheels in which a baby or child
         is pushed around [syn: baby buggy, baby carriage,
         carriage, perambulator, pram, stroller, go-cart,
         pushchair, pusher]