from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun The page size (3.5 by 5.5 inches) that results when a printer's sheet is folded into 32 equal sections.
- noun A book composed of pages of this size.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun printing A paper size, (3.75"-5" x 2.5"-3.125"), one thirty-secondth of an uncut free sheet.
- noun printing A book size, corresponding to the paper size.
from Wiktionary, Creative Commons Attribution/Share-Alike License
Cf the printing terms 32mo (thirty-twomo) & 64mo (sixty-fourmo).
I sought the companionship of several low-browed, ill-favored fellows whom I believed suited to my purposes, but almost immediately I wearied of them, for they had never looked into a book and were so profoundly ignorant as to be unable to distinguish between a folio and a thirty-twomo.