Source : Webster's Revised Unabridged Dictionary (1913)

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

Source : WordNet®

brainish
     adj : 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)}]