All 3 Uses of

elusive

in

Moby Dick

Perhaps they were; or perhaps there might have been shoals of them in the far horizon; but lulled into such an opium-like listlessness of vacant, unconscious reverie is this absent-minded youth by the blending cadence of waves with thoughts, that at last he loses his identity; takes the mystic ocean at his feet for the visible image of that deep, blue, bottomless soul, pervading mankind and nature; and every strange, half-seen, gliding, beautiful thing that eludes him; every dimly-discovered, uprising fin of some undiscernible form, seems to him the embodiment of those elusive thoughts that only people the soul by continually flitting through it.†
Chpt 34-36

of our Lord; though in the Vision of St. John, white robes are given to the redeemed, and the four-and-twenty elders stand clothed in white before the great-white throne, and the Holy One that sitteth there white like wool; yet for all these accumulated associations, with whatever is sweet, and honourable, and sublime, there yet lurks an elusive something in the innermost idea of this hue, which strikes more of panic to the soul than that redness which affrights in blood.†
Chpt 40-42

This elusive quality it is, which causes the thought of whiteness, when divorced from more kindly associations, and coupled with any object terrible in itself, to heighten that terror to the furthest bounds.†
Chpt 40-42 *

Definition:

difficult to get a hold of

(mentally such as a memory or description; or externally such as an achievement or physical capture)