underside
/ˈʌndəsaɪd/noun
1- the bottom or lower side or surface of something下侧; 下面; 底面：
the butterfly's wings have a mottled brown pattern on the underside.
蝴蝶翅膀底面有棕色斑纹。
1.1
- figurative the less favourable aspect of something〈喻〉（事物）阴暗面：
the sordid underside of the glamorous 1980s.
辉煌的20世纪80年代的不光彩一面。