Synonyms of unperturbable

1 Syllable
cool, sure, still, quiet
2 Syllables
tranquil, placid, poised, easy
3 Syllables
confident, nonchalant, serene, peaceful, easygoing, unruffled, sanguine, collected, possessed, together
4 Syllables
unperturbed, levelheaded, unflappable, self-possessed, temperate