1. The first letter of the English alphabet, used to distinguish the first page of a folio from the second, marked b, or the first page of a book, the first foot-note on a printed page, the first of a series of subdivisions, etc., from the following ones, which are marked b, c, d, e, etc.
2. Lat. The letter marked on the ballots by which, among the Romans, the people voted against a proposed law. It was the initial letter of the word "antiquo," I am for the old law. Also the letter inscribed on the ballots by which jurors voted to acquit an accused party. It was the initial letter of "absolvo," I acquit. Tayl. Civil Law, 191, 192.
3. The English indefinite article. This particle is not necessarily a singular term; it is often used in the sense of "any," and is then applied to more than one individual object. National Union Bank v. Copeland, 141 Mass. 267, 4 N. E. 794; Snowden v. Guion, 101 N. Y. 458, 5 N. E. 322; Thompson v. Stewart, 60 Iowa, 225, 14 N. W. 247; Commonwealth v. Watts, 84 Ky. 537, 2 S. W. 123.
Source: Black's Law Dictionary 2nd Ed (1910)