let-down
/ˈletdaʊn/noun
1
- a disappointment失望：
the election was a bit of a let-down.
选举有点儿令人失望。
2
- mass noun the release of milk in a nursing mother or lactating animal as a reflex response to suckling or massage泌乳（妇女哺乳时由授乳动作产生的生理反应, 或母兽放乳时因受按摩而产生的生理反应）。
3
- Aeronautics the descent of an aircraft or spacecraft prior to landing【航空】（飞行器或航天飞机着陆前的）下降。