clearheaded

/ˈklɪrˌ(h)ɛdəd/

If you're clearheaded, you're wide awake, focused, and thinking sensibly. A clearheaded student will probably do better on a calculus test than her sleepy, confused classmate.

Complex thought and analysis ideally requires a clearheaded thinker — and you can also describe the thinking and decisions themselves as clearheaded. A clearheaded debate between political candidates is much more useful and interesting than a muddled, angry, and confusing argument. The word clearheaded, sometimes spelled with a hyphen, clear-headed, originated in the early 18th century.

Definitions of clearheaded

1. adjective

   not mentally confused; able to think clearly and act intelligently
   synonyms: clear-thinking

   clear

   free from confusion or doubt

   unclouded

   not mentally disordered

   antonyms:

   confused

   mentally confused; unable to think with clarity or act intelligently

   addlebrained, addlepated, muddleheaded, puddingheaded

   stupid and confused

   addled, befuddled, muddled, muzzy, woolly, woolly-headed, wooly, wooly-minded

   confused and vague; used especially of thinking

   befogged, befuddled

   stupefied by alcoholic drink

   clouded

   mentally disordered

   dazed, stunned, stupefied, stupid

   in a state of mental numbness especially as resulting from shock

   dazzled

   stupefied or dizzied by something overpowering

   trancelike

   as if in a trance

   punch-drunk, silly, slaphappy

   dazed from or as if from repeated blows

   spaced-out

   confused or disoriented as if intoxicated through taking a drug

   perplexed

   full of difficulty or confusion or bewilderment