The Collaborative International Dictionary of English v.0.48:

ladder-back \ladder-back\ n.
   a chair with a ladder-back[2].

   Syn: ladder-back chair.
        [WordNet 1.5]

   2. a chair backrest consisting of 2 uprights with several
      connecting slats.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

ladder-back
    n 1: a chair with a ladder-back [syn: ladder-back, ladder-
         back chair]
    2: the backrest of a chair that consists of two uprights with
       connecting slats