1. [n]  someone or something that is abnormally large and powerful
2. [n]  (Old Testament) a giant Philistine warrior who David slayed with a slingshot

Goliath
When a new US-designed super submarine is commandeered by a renegade Russian computer genius, it falls to Army captain Gunner Wolfe--who is aboard the sub--to set things right.

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great. (1.) A famous giant of Gath, who for forty days openly defied the armies of Israel, but was at length slain by David with a stone from a sling (1 Sam. 17:4). He was probably descended from the Rephaim who found refuge among the Philistines after they were dispersed by the Ammonites (Deut. 2:20, 21). His height was "six cubits and a span," which, taking the cubit at 21 inches, is equal to 10 1/2 feet. David cut off his head (1 Sam. 17:51) and brought it to Jerusalem, while he hung the armour which he took from him in his tent. His sword was preserved at Nob as a religious trophy (21:9). David's victory over Goliath was the turning point in his life. He came into public notice now as the deliverer of Israel and the chief among Saul's men of war (18:5), and the devoted friend of Jonathan.

(2.) In 2 Sam. 21:19 there is another giant of the same name mentioned as slain by Elhanan. The staff of his apear "was like a weaver's beam." The Authorized Version interpolates the words "the brother of" from 1 Chr. 20:5, where this giant is called Lahmi.