Reticent (adjective)

1. Being reserved or reluctant to express one's thoughts, feelings, or opinions.
2. Being unwilling to speak freely or openly.
3. Being quiet or reserved in manner or speech.

Origin:

From latin 'reticere' meaning 'to keep silent'.

Examples:

1. She was reticent about her personal life, preferring to keep her private matters private.
2. He was reticent in the meeting, only speaking when directly addressed.
3. Despite her success, she remains reticent about her achievements, always giving credit to her team.
4. The reticent witness refused to answer any questions about the incident.
5. The reticent cat hid under the bed when guests came over.