From Longman Dictionary of Contemporary Englishequanimityeq‧ua‧nim‧i‧ty /ˌiːkwəˈnɪməti, ˌekwə-/ noun [uncountable] formalCALM calmness in the way that you react to things, which means that you do not become upset or annoyed He received the news with surprising equanimity.
Examples from the Corpus
equanimity• Jennifer explains this with an equanimity that characterises her.• He had a kind of gentleness and equanimity.• This apparent equanimity, however, is belied by evidence that health and health care are major concerns of older people.• She supposed it gave him his equanimity.• In time, she attained, if not virtue, a modicum of equanimity.• Lying in clouds of scent in the sunken tub filled to the brim, that streak of equanimity she had asserted itself.• Hess, however, took it with equanimity, and laughed at Edward's own unease.• His parents took the news with equanimity.Origin equanimity (1600-1700) Latin aequanimitas, from aequo animo “with level mind” 