By-accident meaning : Accidental; as the result of some unforeseen happening or series of events; unexpected; resulting from an event without the foresight, expectation, aid, or design of the person by whose agency it was caused; unintentional. Accidentally; unintentionally; without meaning to; as the result of an event not expected, aided, or willingly planned. As the result of some undesigned, unintended, unrelated, natural, or random occurrence; as the unexpected and unforeseen result of formerly unrelated factors. By chance; unexpectedly; as the result of an unrelated series of events.