Vigesimo-quarto

Vi`ges´i`mo-quar´to


a.1.Having twenty-four leaves to a sheet; as, a vigesimo-quarto form, book, leaf, size, etc.
n.1.A book composed of sheets each of which is folded into twenty-four leaves; hence, indicating more or less definitely a size of book so made; - usually written 24mo, or 24°.
Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.