Dictionary.net

characterized by a lack of openness esp about one's actions or purposes

characterized by a lack of openness (especially about one's actions or purposes)

The faculty or propensity which impels to reserve, secrecy, or concealment.

The faculty or propensity which impels to reserve, secrecy, or concealment.

n. The quality of being secretive; —in phrenology, a bump or organ situated at the inferior margin of the parietal bones, which when large or fully developed, is said to Impel the individual to concealment or secrecy.