1. (adverb)unexpectedly, out of the blue in a way that was not expected Synonyms: circumstantially, unexpectedly, accidentally, out of the blue, by chance
2. (adverb)by chance, accidentally, circumstantially, unexpectedly without advance planning Synonyms: by luck, incidentally, unintentionally, accidentally, circumstantially, perchance, by chance, unexpectedly, out of the blue, haply, minutely