incomprehensible, primal, hard, healthy, cloggy, hidden, intimate, sonorous, dusky, unfathomed, cardinal, grave, obscure, great, indistinct, dark, underlying, sound, punishing, well-grounded, serious, gruelling, impenetrable, surface, recondite, expectant, turbid, large, with child, gravid, operose, difficult, doubtful, enlightened, silent, significant, effectual, enceinte, heavy, involved, fleshy, reflective, superficial, big, heartfelt, shallow, sullen, labored, backbreaking, esoteric, overweight, intemperate, toilsome, mysterious, ambiguous, grievous, threatening, sage, enigmatical, lowering, strong, unplumbed, intricate, leaden, dim, rudimentary, dense, good, informed, weighty, weighed down, complicated, levelheaded, abstruse, darksome, reasoned, ponderous, complex, intense, arduous, muddy, grueling, laborious, unintelligible, unsounded, subterranean, thoughtful, clayey, important, lumbering, key, fundamental, easy, cloudy, laboured, learned, legal, solemn, wakeless, level-headed, discerning, central, thorough, penetrating, scholarly
deep (part of speech: adjective)
intelligent (part of speech: adjective)
comprehending, perspicacious, intelligent, erudite, astute, knowing, gifted, encyclopedic, capable, canny, sophisticated, sharp, knowledgeable, worldly, bright, clever, genius, cogent, sagacious, wise, smart, brilliant, brainy, intellectual
- He finds the most profound thing in all the world to be the universal spiritual life. - "The Approach to Philosophy", Ralph Barton Perry.
- It was not a very profound thought. - "The Heart of Unaga", Ridgwell Cullum.
- The rest of the company simply stared in the most profound silence at Walter. - "The High Calling", Charles M. Sheldon.