[countable] a period of time when the level of sth is low, especially a time when a business or the economy is not growing
低谷；（企业或经济的）萧条阶段，低潮◆The rate fell to a trough of 3% last year.
去年增长率降至 3% 的谷底。◆The pension fund invested in bonds to avoid the peaks and troughs of the stock market.
退休基金投资於债券以避开股票市场的时起时落。 OPP peak  ➡  picture at business cycle