• Webster's Revised Unabridged Dictionary
    • a Twenty-fourmo Having twenty-four leaves to a sheet; as, a twenty-fourmo form, book, leaf, size, etc.
    • ***
Century Dictionary and Cyclopedia
    • n twenty-fourmo A leaf from a sheet of paper regularly folded for a book in twenty-four equal parts. When the size of paper is not named, it is supposed to be a medium 24mo, of which the untrimmed leaf is about 3⅝ by 5⅛ inches.
    • n twenty-fourmo A book made up of leaves folded in twenty-four equal parts.
    • n twenty-fourmo Usually written 24 mo.
    • ***