Persistently calm, whether when facing difficulties or experiencing success; not easily upset or excited.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "unflappable" in a sentence
"The word unflappable has been used, correctly, and that puts him in contrast to the incumbent, who often seems not so much calm as insensate."
"The Penguins 'coach, Dan Bylsma, says the level of hatred was so lacking as his team - which only the day before he had called "unflappable" - flapped badly against the Senators, that they had better find some by tonight's Game 2 in Pittsburgh."
"Why oh why oh why did the Yankees think it was wise to pay $82.5 million to this 34-year-old pitcher, who has proven himself so unreliable and ineffective that the mere mention of his name causes unflappable New Yorkers to seethe?"