Sagacious, a.
Etymology: [L. sagax, sagacis, akin to sagire to perceive quickly or keenly, and probably to E. seek. See Seek, and cf. Presage.]
1. Of quick sense perceptions; keen-scented; skilled in following a trail. Sagacious of his quarry from so far. Milton.
2. Hence, of quick intellectual perceptions; of keen penetration and judgment; discerning and judicious; knowing; far-sighted; shrewd; sage; wise; as, a sagacious man; a sagacious remark. Instinct . . . makes them, many times, sagacious above our apprehension. Dr. H. More. Only sagacious heads light on these observations, and reduce them into general propositions. Locke.
Syn. -- See Shrewd. -- Sa*ga"cious*ly, adv. -- Sa-ga"cious*ness, n.
Shades of meaning
Sagacious refers to a power of tracing the hidden or recondite by slight indications, as by instinct or intuition; it is not now applied to mere keenness of sense-perception. We do not call a hound sagacious in following a clear trail; but if he loses the scent, as at the edge of a stream, and circles around till he strikes it again, his conduct is said to be sagacious. In human affairs sagacious refers to a power of ready, far-reaching, and accurate inference from observed facts perhaps in themselves very slight, that seems like a special sense; or to a similar readiness to foresee the results of any action, especially upon human motives or conduct--a kind of prophetic common sense. Sagacious is a broader and nobler word than shrewd, and not capable of the invidious sense which the latter word often bears; on the other hand, sagacious is less lofty and comprehensive than wise in its full sense, and more limited to matters of direct practical moment. Compare astute; wisdom.