the GNU version of the Collaborative International Dictionary of English
adj. Cautious in speaking; secret; wary; uncommunicative.
The Century Dictionary and Cyclopedia
Sparing of speech; reticent: as, a close-mouthed person.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. inclined to secrecy or reticence about divulging information
Word Usage
"Though Declan had become an expert at torture, the immortals were astonishingly closemouthed, even withholding information about their natural enemies."