Synonyms for Secret:

adj.

all (adjective)
unavowed.
cloak-and-dagger (adjective)
hugger mugger.
concealed (adjective)
cloaked, camouflaged, disguised, stealthy, masked, censored, hush-hush, concealed, hidden, buried, Screened, enshrouded, covert, anonymous, Obscured.
deep (adjective)
orphic.
hidden, unrevealed (adjective)
secluded, covert, occult, furtive, unintelligible, hush-hush, strange, private, closet, mystical, disguised, camouflaged, underground, unenlightened, classified, close, mystic, ambiguous, clouded, mysterious, esoteric, arcane, cloak-and-dagger, undercover.
private (adjective)
exclusive, esoteric, personal, intimate, confidential, inward, private.
secluded (adjective)
Screened.
secret (adjective)
restricted, covert, stealthy, clandestine, furtive, hush-hush, arcane, classified, confidential.
top-secret (adjective)
classified.
underhand (adjective)
on the quiet.
underhand, clandestine (adjective)
underhanded, sly, inside, secretive, stealthy, restricted, unacknowledged, incognito, confidential, surreptitious.

n.

way, show, method, procedure, system, mode, technique, manner, basis, tactic. sub rosa, shadowy, huggermugger, in strict confidence. auricular, inside. key, formula, ticket, route, means. discovery (noun)
formula.
hidden (noun)
latent.
secret (noun)
enigma, hugger mugger, concealed, hole-and-corner, hush-hush, covert, underground, confidential, mystic, mystery, hidden, mysterious, undercover, arcanum, unacknowledged, private, cloak-and-dagger, secluded, mystical, occult, classified, esoteric, inward, closed book, privy, unavowed, surreptitious, on the quiet, closet, orphic, clandestine.
something kept hidden, unrevealed (noun)
mystery, puzzle, key, confidence, formula, enigma.

Other synonyms:

secrecy, confidentiality, strange, trade secret, unknown quantity, auricular, hidden agenda, conspiracy of silence, underhanded, state secret, secretive, shadowy. intimacy, confidence, perplexity, puzzle. inside, uncertainty. formula, key. route. ticket. thing. ambiguous
enigmatic.
camouflaged
incognito.
secretive
sly.
Other relevant words:
closed book, route, hugger mugger, secrecy, secretive, key, close, perplexity, unenlightened, strange, huggermugger, technique, unintelligible, ambiguous, arcanum, ticket, unavowed, on the quiet, confidentiality, latent, surreptitious, enigma, unacknowledged, shadowy, mysterious, underground, clouded, puzzle, thing, auricular, occult, enigmatic, cloak-and-dagger, mystic, mystery, mystical, undercover, orphic, incognito, underhand, inward, inside, underhanded, sly, closet, privy, confidence, secluded, formula, hole-and-corner.

Usage examples for secret

  1. And that is-" "- His secret – The Complete Project Gutenberg Works of George Meredith by George Meredith
  2. It would be so wonderful to have this as a secret of our own and see what we can make of it. – The Dragon's Secret by Augusta Huiell Seaman
  3. Noll Wing, strong man and brave, could not hide his secret from her.... – The Sea Bride by Ben Ames Williams