[1] : The Collaborative International Dictionary of English v.0.48

clear-headed \clear"-head`ed\ kl=er"he^d`e^d, a.
   having a clear understanding; quick of perception;
   intelligent. "he was laborious and clear-headed." --macaulay.
   -- clear"-head`edness, n.
   1913 webster
see also:
clear"-head`edness 

[2] : WordNet (r) 2.0

clearheaded
     adj : not mentally confused; able to think clearly and act
           intelligently syn: clear-thinking ant: confused
see also:
clear-thinking confused 

Clearheaded >> C Words
Clearheaded, definition of term: Clearheaded
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