From BiblePortal Wikipedia

Wilson's Dictionary of Bible Types [1]

 Judges 3:14 (c) Ten is the number of human weakness and defeat, Eight is the number of a new beginning. The number of "eighteen," therefore, indicates deliverance from defeat and the beginning of new liberty.

 Judges 10:8 (c) The Philistines and the Ammonites "oppressed the children of Israel eighteen years." This period of weakness was ended by the beginning of victory and deliverance.

 2 Kings 24:8 (c) This lad was eighteen years of age. He had the years of weakness and he had the beginning of something new, for the King of Babylon came and carried him into captivity.

 Luke 13:11 (c) This woman also had a period of helplessness and had the joy of seeing a new experience come into her life and soul when Jesus spoke. See also  Luke 13:4. When their sinning ended, their suffering began.

Webster's Dictionary [2]

(1): ( n.) A symbol denoting eighteen units, as 18 or xviii.

(2): ( a.) Eight and ten; as, eighteen pounds.

(3): ( n.) The number greater by a unit than seventeen; eighteen units or objects.

King James Dictionary [3]

Eighteen, a 'ateen. Eight and ten united.