The Collaborative International Dictionary of English v.0.48:
Heir \Heir\ ([^a]r), n. [OE. heir, eir, hair, OF. heir, eir, F.
hoir, L. heres; of uncertain origin. Cf. Hereditary,
1. One who inherits, or is entitled to succeed to the
possession of, any property after the death of its owner;
one on whom the law bestows the title or property of
another at the death of the latter.
I am my father's heir and only son. --Shak.
2. One who receives any endowment from an ancestor or
relation; as, the heir of one's reputation or virtues.
And I his heir in misery alone. --Pope.
Heir apparent. (Law.) See under Apparent.
Heir at law, one who, after his ancector's death, has a
right to inherit all his intestate estate. --Wharton (Law
Heir presumptive, one who, if the ancestor should die
immediately, would be his heir, but whose right to the
inheritance may be defeated by the birth of a nearer
relative, or by some other contingency.
Bouvier's Law Dictionary, Revised 6th Ed (1856):
HEIR AT LAW. He who, after his ancestor's death intestate, has a right to
all lands, tenements, and hereditaments, which belonged to him, or of which
he was seised. The same as heir general. (q.v.)