9 letters · 16 points in Scrabble
adjective having or revealing little emotion or sensibility; not easily aroused or excited; ; - Nordhoff & Hall; -Virginia Woolf
adjective deliberately impassive in manner
originFrom im- (prefix meaning ‘not’) + passive (“which is, or is capable of being, acted on; (obsolete) which suffers, or may suffer, pain, death, etc.”, adjective).
Etymology from Wiktionary, CC BY-SA 3.0