Tasaciturn

I got this word from word of the day of dictionary.com.

taciturn \TAS-uh-turn\, adjective:

Habitually silent; not inclined to talk.

On stage she seemed to become transformed, and the contrast was even more noticeable given her shy, taciturn character, shrouded in the impalpable veil of gloom that always surrounded her.
-- Pino Cacucci, Tina Modotti: A Life

A balding, stocky, taciturn man who wore glasses, he gave an impression of distance and seriousness.
-- "Diana's Driver: Unsettling Piece in a Puzzle", New York Times, September 21, 1997

In the company of even his close literary and political friends he was shy if not taciturn.
-- "Passionate voice of the press", Irish Times, November 4, 1997

Taciturn comes from Latin taciturnus, from tacere, "to be silent."