brainish

from WordNet (r) 3.0 (2006)

brainish
    adj 1: characterized by undue haste and lack of thought or
           deliberation; "a hotheaded decision"; "liable to such
           impulsive acts as hugging strangers"; "an impetuous
           display of spending and gambling"; "madcap escapades";
           (`brainish' is archaic) [syn: {hotheaded}, {impulsive},
           {impetuous}, {madcap}, {tearaway(a)}, {brainish}]

from The Collaborative International Dictionary of English v.0.48

Brainish \Brain"ish\, a.
   Hot-headed; furious. [R.] --Shak.
   [1913 Webster]