Taciturn (adjective)

1. Not inclined to talk or speak, especially habitually.
2. Reserved or reticent in speech; saying little.
3. Not expressing one's thoughts or feelings easily.

Origin:

From latin taciturnus, from tacere "to be silent".

Examples:

1. He was known for being taciturn and not speaking much.
2. She found him to be too taciturn for her taste.
3. He was a taciturn person who kept to himself.
4. The taciturn nature of the employee made communication difficult.
5. He was a taciturn listener, never interrupting or contributing much to the conversation.