wise man(n = noun.person) mentor - a wise and trusted guide and advisor;

N  sage, wise man, genius, master mind, master spirit of the age, longhead, thinker, intellectual, longhair, authority, oracle, luminary, shining light, esprit fort, magnus Apollo, Solon, Solomon, Nestor, Magi, second Daniel, man of learning, expert, wizard, wiseacre, bigwig, know-it-all, poor man's Einstein, venerable, reverenced, emeritus, barba tenus sapientes.