[1] : The Collaborative International Dictionary of English v.0.48

pacer \pa"cer\, n.
   one who, or that which, paces.
   1913 webster

   2. especially: a horse trained to a special gait in which
      both feet on one side leave the ground together; a horse
      that paces. wordnet sense 2
      wordnet 1.5

   3. a horse used to set the pace in racing. wordnet sense 3

   syn: pacemaker, pacesetter.
        wordnet 1.5

[2] : WordNet (r) 2.0

pacer
     n 1: a horse used to set the pace in racing syn: pacemaker, pacesetter
     2: a horse trained to a special gait in which both feet on one
        side leave the ground together
see also:
pacemaker pacesetter 

[3] : Virtual Entity of Relevant Acronyms (Version 1.9, June 2002)

pacer
     public access to court electronic records
     
     

Pacer >> P Words
Pacer, definition of term: Pacer
pacer_pag1.html