A (3)

A (ȧ), prep. [[Abbreviated form of an (AS. on). See On.]] 1. 1. In; on; at; by. “A God's name.” “Torn a pieces.” “Stand a tiptoe.” “A Sundays” Shak. “Wit that men have now a days.” Chaucer. “Set them a work.” Robynson (More's Utopia).
2. 2. In process of; in the act of; into; to; — used with verbal substantives in -ing which begin with a consonant. This is a shortened form of the preposition an (which was used before the vowel sound); as in a hunting, a building, a begging. “Jacob, when he was a dying” Heb. xi. 21. “We'll a birding together.” “ It was a doing.” Shak. “He burst out a laughing.” Macaulay. The hyphen may be used to connect a with the verbal substantive (as, a-hunting, a-building) or the words may be written separately. This form of expression is now for the most part obsolete, the a being omitted and the verbal substantive treated as a participle.