on purpose Antonyms

accidentally unknowingly by luck by mistake by accident coincidentally unconsciously unwittingly by coincidence by a quirk of fate by reflex by a happy chance by a mere chance by a twist of fate by pure chance by sheer chance haphazardly fortuitously inadvertently automatically circumstantially instinctively intuitively involuntary mechanically perchance perforce randomly unawares spontaneously by chance unexpectedly unintentionally incidentally in a random way