Black's Law Dictionary (2nd edition)dictionaries

In Being

In existence or life at a giv-en moment of time, as, in the phrase “life or lives in being” in the rule against per-petnities. An unborn child may, in some circumstances be considered as “in being.” Phillips v. Herron, 55 ohio St. 478, 45 N, E. 720; Hone v. Van Schalck, 3 Barb. Ch. (N. Y.) 509

Source: Black’s Law Dictionary 2nd Ed (1910)