adj. 25B6; adjective
subtle colours : UNDERSTATED, muted, subdued; delicate, faint, pale, soft, indistinct.
subtle distinctions : FINE, fine-drawn, nice, overnice, hair-splitting.
a subtle mind : ASTUTE, keen, quick, fine, acute, sharp, shrewd, perceptive, discerning, discriminating, penetrating, sagacious, wise, clever, intelligent.
a subtle plan : INGENIOUS, clever, cunning, crafty, wily, artful, devious.