Sentence:  ... Ahab rapidly ordered the ship's course to be slightly altered, and the sail to be shortened. The <WSD>acute</WSD> policy dictating these movements was sufficiently vindicated at daybreak, by the sight of a long sleek on the sea directly and lengthwise ahead, smooth as oil, and resembling in the pleated watery wrinkles bordering it, the polished metallic-like marks of some swift tide-rip, at the mouth of a deep, rapid stream. 
Meaning of the word marked with <WSD> tags:  Urgent.