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 ...
deadpan: deliberately impassive in manner; "deadpan humor"; "his face remained expressionless as the verdict was read"
(impassively) in an impassive manner; "he submitted impassively to his arrest"
(impassiveness) emotionlessness: apathy demonstrated by an absence of emotional reactions
Apathy (also called impassivity or perfunctoriness) is a state of indifference, or the suppression of emotions such as concern, excitement, motivation and passion. An apathetic individual has an absence of interest in or concern about emotional, social, or physical life. ...
Having, or revealing, no emotion; Still or motionless
(adj.) stoic, not susceptible to suffering (Stop being so impassive; it’s healthy to cry every now and then.)