(adv.) In an impulsive manner.

a corps perdu abruptly at half cock bang capriciously chaotically dash erratically every which way hastily head over heels headfirst headforemost headlong heels over head helter-skelter higgledy-piggledy impetuously in a rush inconsistently inconstantly irregularly like a flash like a thunderbolt nonuniformly of a sudden on short notice overhastily oversoon plop plump plunk pop precipitantly precipitately precipitously prematurely quickly rashly recklessly sharp slap slap-bang smack spasmodically sporadically startlingly sudden suddenly surprisingly too early too soon unawares unequally unevenly unexpectedly unsteadily unsystematically untimely ununiformly without notice without warning