The Collaborative International Dictionary of English v.0.48:

Temerarious \Tem`er*a"ri*ous\, a. [L. temerarius. See
   Temerity.]
   Unreasonably adventurous; despising danger; rash; headstrong;
   audacious; reckless; heedless. -- Tem`er*a"ri*ous*ly, adv.
   [1913 Webster]

         I spake against temerarious judgment.    --Latimer.
   [1913 Webster]