| furtive(adjective, dishonest, deceitful, hidden, sly) |
| arcanum(noun, mystery) |
| obscure(adjective, quiet, dark, superior, strange) |
| inherent(adjective, intimate, private, mental, hidden) |
| innermost(adjective, intimate, private, inside, personal) |
| brain-teaser(noun, trouble, challenge, question, puzzle) |
| classified(adjective, close, sensitive, intimate, private) |
| intrinsic(adjective, intimate, private, mental, hidden) |
| profound(adjective, hard, obscure, deep, thoughtful) |
| undisclosed(adjective, unknown, hidden, personal, concealed) |
| underhand(adjective, dishonest, deceitful, hidden, sly) |
| abstruse(adjective, evil, obscure, dark, strange) |
| close(adjective, quiet, humble, shy, distant) |
| deep-seated(adjective, intimate, private, mental, penetrating) |
| hugger-mugger(adjective, quiet, intriguing) |
| secretive(adjective, quiet, mean, smooth, obscure) |
| sneaky(adjective, close, clandestine, latent, underhand) |
| visceral(adjective, remote, intimate, private, inside) |
| disguised(adjective, obscure, unknown, hidden, clandestine) |
| enigmatic(adjective, evil, obscure, property, strange) |