imperturbable

adjective

अविचलित; शान्त

not easily perturbed or excited or upset; marked by extreme calm and composure

hitherto imperturbable, he now showed signs of alarm
अहिलेसम्म शान्त रहेको ऊ अब आत्तिन थाल्यो

an imperturbable self-possession
अविचलित आत्मसंयम