Format \For`mat"\ (f[-o]r`m[.a]" or f[-o]r`m[aum]t"), n. [F. or G. Cf. Formation.]

(Print.) The shape and size of a book; hence, its external form.

The older manuscripts had been written in a much larger format than that found convenient for university work. --G. H. Putnam.

One might, indeed, protest that the format is a little too luxurious. --Nature.

Source: Webster's Revised Unabridged Dictionary (1913)