done secretly; kept secret

secret, sly

(of glances, threats etc) hidden; disguised

clandestine, underhanded

of hide

unseen, secret

disguised; with one's name

in disguise

not striking or obvious

hidden, unnoticeable

that cannot be seen

unable to be seen; hidden

present but not yet active, developed or visible

dormant, hidden

hidden; not clearly seen; not easily understood; not well known

not easily understood

a rude or unpleasant person

obscure, mysterious

of something that is not controlled or explained by physical laws

mysterious, not of this world

beyond what is first seen or said

secret; pertaining to a hidden goal

acting secretly

secret, spy

deceitful(ly)

deceitful

basic; hidden but able to be found

fundamental, latent

not known or identified

obscure, mysterious

not easily seen or noticed

inconspicuous

not publicly acknowledged

in disguise

not seen

hidden