IMPASSIVE
deadpan, expressionless, impassive, poker-faced, unexpressive
(adjective) deliberately impassive in manner; “deadpan humor”; “his face remained expressionless as the verdict was read”
impassive, stolid
(adjective) 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”
Source: WordNet® 3.1
Etymology
Adjective
impassive (comparative more impassive, superlative most impassive)
Having, or revealing, no emotion.
Still or motionless.
Synonyms
• apathetic, phlegmatic
Source: Wiktionary
Im*pas"sive, a.
Definition: Not susceptible of pain or suffering; apathetic; impassible;
unmoved.
Impassive as the marble in the quarry. De Quincey.
On the impassive ice the lightings play. Pope.
– Im*pas"sive*ly, adv.
– Im*pas"sive*ness, n.
Source: Webster’s Unabridged Dictionary 1913 Edition