keen

keen adjective acute, aggressive, all fired-up, all out, ambitious, animated, anxious, ardent, assiduous, avid, brisk, burning, committed, deep, deep-felt, desirous, disposed, dynamic, eager, earnest, ebullient, enterprising, enthused, enthusiastic, excited, exuberant, fervent, fervid, feverish, fiery, flaming, full of enthusiasm, heartfelt, hearty, heated, intense, intent, obsessed, passionate, pliant, proactive, profound, prompt, quick, raring to, ready, receptive, responsive, robust, vibrant, vigorous, vital, vivacious, vivid, zealous, zestful

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See also: acute, bitter, close, cognizant, discerning, discriminating, eager, fervent, incisive, intense, judicious, perceptive, perspicacious, ready, receptive, responsive, sapient, sedulous, sensitive, sly, solicitous, subtle, trenchant, willing, zealous