The Collaborative International Dictionary of English v.0.48:

Trigesimo-secundo \Tri*ges"i*mo-se*cun"do\, n.
   A book composed of sheets so folded that each one makes
   thirty-two leaves; hence, indicating, more or less
   definitely, a size of book; -- usually written 32mo, or
   32[deg], and called thirty-twomo.
   [1913 Webster]