by chance

偶然，碰巧

buxom, buy, buy off, buy out, buy up, buyer, buzz, buzz off, buzz-word, buzzard, buzzer, by, by accident, by air, by all means, by all nerves, by analogy, by and by, by and large, by any means, by choice, by comparison, by courtesy of, by error, by far, by force, by hand, by heart, by instinct, by invitation, by itself, by leaps and bounds, by little and little, by means of, by mistake, by name, by nature, by night, by no means, by oneself,