N-COUNT [usually singular, oft NOUN n]先兆;征兆;风向标 If you describe something as a bellwether, you mean that it is an indication of the way a situation is changing. 先兆;征兆;风向标 [mainly US, journalism]
For decades the company was the bellwether of the British economy.
几十年来,这家公司一直是英国经济的晴雨表。
IBM is considered the bellwether stock on Wall Street.