unruffable

unruffable

(ʌnˈrʌfəbəl)
adj
implacable
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in classic literature ?
But people who go voluntarily to law, or are taken forcibly there, for the first time, may be allowed to labour under some temporary irritation and anxiety; and Sam, with a due allowance for the frailties of human nature, obeyed all his master's behests with that imperturbable good-humour and unruffable composure which formed one of his most striking and amiable characteristics.
THE normally unruffable Lord Jones of Birmingham (pictured) was left a little embarrassed with a high profile gaff in the House of Lords.
Usually unruffable, Joe was understandably swearing afterwards.