impassive im-PASS-iv, adjective:

1. Devoid of or unsusceptible to emotion.
2. Showing no sign of emotion or feeling; expressionless.


As before, he seemed neither happy nor unhappy. Just utterly impassive.
-- Lesley Hazleton, Driving To Detroit

Yet highway troopers, too, wore smoked glasses to mask their emotions and thus look formidably impassive as they delivered news as highly charged as jazz.
-- Edward Hoagland, Compass Points

He was a slight, kindly man, his impassive face sculpted with deep furrows, who held himself very erect and had a demeanor which suggested a degree of resigned boredom from having taught the same unchanging discipline year after year to each new class of medical students.
-- Frances K. Conley M.D., Walking Out on the Boys

Still, he remained impassive and unexcited, even when informed of the death of Helen Jewett.
-- Patricia Cline Cohen, The Murder of Helen Jewett

Impassive is derived from Latin in-, "not" + passivus, "subject to emotion," from passus, past participle of pati, "to suffer."