cool-headed

from The Collaborative International Dictionary of English v.0.48

cool-headed \cool"-head`ed\, coolheaded \cool"head*ed\, a.
   Having a temper not easily excited; free from passion;
   unshakably calm and collected. -- {Cool"-head`ed*ness}, n.

   Syn: cool, imperturbable, unflappable.
        [1913 Webster + WordNet 1.5]