secretive

Concise Oxford English Dictionary © 2008 Oxford University Press:
secretive/ˈsiːkrətɪv/

▶adjective inclined to conceal feelings and intentions or not to disclose information.

– derivatives
secretively adverb,
secretiveness noun.

– origin C19: back-form. from secretiveness, suggested by Fr. secrétivité, from secret ‘secret’.