The term 'calm and impassive' can be summarized as 'STOLID', which is a six-letter word meaning 'showing little or no emotion; unemotional'. STOLID people are often seen as being unresponsive and indifferent to their surroundings. They may appear to be unaffected by events, even when they are actually feeling something inside. This type of behavior is often seen as a sign of strength and resilience in the face of adversity.