MOST ASTUTE is a term used to describe someone who is exceptionally intelligent and perceptive. The crossword solutions KEENEST (7 letters), CANNIEST (8 letters) and SHREWDEST (9 letters) all refer to this same quality of being astute. KEENEST implies sharpness and acuteness, CANNIEST suggests craftiness and resourcefulness, and SHREWDEST implies wisdom and insight. All three words are synonyms for MOST ASTUTE.