From BiblePortal Wikipedia

King James Dictionary [1]

Poster'Ity, n. L. posteritas, from posterus, from post, after.

1. Descendants children, children's children, &c. indefinitely the race that proceeds from a progenitor. The whole human race are the posterity of Adam. 2. In a general sense, succeeding generations opposed to ancestors.

To the unhappy that unjustly bleed,

Heav'n gives posterity t' avenge the deed.

Webster's Dictionary [2]

(1): ( n.) Succeeding generations; future times.

(2): ( n.) The race that proceeds from a progenitor; offspring to the furthest generation; the aggregate number of persons who are descended from an ancestor of a generation; descendants; - contrasted with ancestry; as, the posterity of Abraham.