underlyingEnglishOxford American Thesaurusunderlying adjective 1 he took issue with the underlying aims of the research: fundamental, basic, basal, primary, prime, first, cardinal, central, principal, chief, key, elementary, elemental, rudimentary, root, intrinsic, essential. ▷antonyms subordinate. 2 she spoke airily despite an underlying feeling of irritation: latent, lurking, repressed, suppressed, unrevealed, undisclosed, unexpressed, undivulged, concealed, hidden, veiled, masked, shrouded, under wraps. ▷antonyms overt.