impassive \im-PASS-iv\ (adjective) - 1 : Devoid of or unsusceptible to emotion. 2 : Showing no sign of emotion or feeling; expressionless.

"Don Corleone listened like a priest in the confessional, gazing away into the distance, impassive, remote." --Mario Puzo, 'The Godfather'

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