madcap

Adjective

• characterized by undue haste and lack of thought or deliberation; (`brainish' is archaic)
  • a hotheaded decision
    
  • liable to such impulsive acts as hugging strangers
    
  • an impetuous display of spending and gambling
    
  • madcap escapades
    

Noun

• a reckless impetuous irresponsible person

Related words

• Synonyms: 
  hotheaded , impulsive , impetuous , tearaway(a) , brainish , daredevil , hothead , swashbuckler , lunatic , harum-scarum