impassive

(s) having or revealing little emotion or sensibility; not easily aroused or excited
- her impassive remoteness
- "he remained impassive, showing neither interest in nor concern for our plight"- Nordhoff & Hall
- "a silent stolid creature who took it all as a matter of course"-Virginia Woolf
- her face showed nothing but stolid indifference
stolid,
(s) deliberately impassive in manner
- deadpan humor
- his face remained expressionless as the verdict was read
deadpan, expressionless, poker-faced, unexpressive,

stolid deadpan expressionless poker-faced unexpressive

impassively impassiveness