calm; not easily perturbed or excited or upset; marked by extreme calm and composure
His imperturbable demeanor remained steady throughout the crisis.
Vocabulary like imperturbable appears on the Digital SAT in Words-in-Context questions, where you choose the word that fits a passage's meaning and tone. You can also drill this word with vocabulary flashcards.
expressionless; having or revealing little emotion or sensibility
faultless; without fault or error
penniless; not having enough money to pay for necessities
hinder; be a hindrance or obstacle to
force; urge or force (a person) to an action; constrain or motivate
unnoticeable; impossible or difficult to perceive by the mind or senses
extremely dense; preventing especially liquids to pass or diffuse through
disrespectful; characterized by a lightly pert and exuberant quality