Synonyms for Perspicacious (same or very similar meaning)
WordNet sense 1 (acutely insightful and wise):
sagacious, sapientWordNet sense 2 (mentally acute or penetratingly discerning):
clear-sighted, clear-eyedWordNet sense 3 (having or revealing keen insight and good judgment):
discerningFrom the ODE community, based on WordNetadd/edit