adv. 25B6; adverb BY ACCIDENT, by chance, by a mere chance, by a twist of fate, as luck would have it, fortuitously, by a fluke, by happenstance, coincidentally, adventitiously; unexpectedly, unintentionally, inadvertently, unwittingly.
ACCIDENTALLY
Meaning of ACCIDENTALLY in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012