Synonyms of the word

taciturn

• adj. Silent; temperamentally untalkative; disinclined to speak.

buttoned-up

• adj. Conservative.
• adj. Carefully planned and executed.

concise

• adj. brief, yet including all important information.
• v. (India, transitive) To make concise; to abridge or summarize.

incommunicative

• adj. Uncommunicative.

reticent

• adj. Keeping one's thoughts and opinions to oneself; reserved or restrained.
• adj. (proscribed) Hesitant or not wanting to take some action; reluctant (usually followed by to and a verb…

uncommunicative

• adj. Tending not to communicate; not communicating.

untalkative

• adj. unwilling to talk; taciturn; refusing to speak.