undauntable

un·daunt·a·ble

 (ŭn-dôn′tə-bəl, -dän′-)
adj.
Not admitting of discouragement: undauntable heroism; undauntable optimism.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

undauntable

(ʌnˈdɔːntəbəl)
adj
persistently courageous
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
References in periodicals archive ?
It lights the dark of this prison cell,It thunders forth its might,It is 'the undauntable thought', my friend,That thought that says 'I'm right!'
"The proof of this, so often and so tragically forgotten, is that the costs of providing an undauntable defense, whatever they may be, pale before blood and defeat.
"Viva Cisco" is about an undauntable parrot by the name of Cisco.
as undauntable, generous, and filled with an honor that they absorbed
"She was incorrigible and undauntable. She was all about building this company."