1. 
[syn: hotheaded, impulsive, impetuous, madcap, tearaway(a), brainish]
The Collaborative International Dictionary of English v.0.48:
Brainish \Brain"ish\, a.
   Hot-headed; furious. [R.] --Shak.
   [1913 Webster]
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]