adj. 25B6; adjective
his face was expressionless : INSCRUTABLE, deadpan, poker-faced; blank, vacant, emotionless, unemotional, inexpressive; glazed, stony, wooden, impassive.
a flat, expressionless tone : DULL, dry, toneless, monotonous, boring, tedious, flat, wooden, unmodulated, unvarying, devoid of feeling/emotion.
expressive, lively.