Double denim – a style of dress in which a denim jacket or shirt is worn with a pair of jeans or a denim skirt, often regarded as a breach of fashion etiquette.

双牛仔——指一种穿衣风格，用牛仔夹克或牛仔T恤配牛仔裤或牛仔裙，这种搭配通常被认为是违背时尚标准的。

Example:

Wearing a suit and no socks is a cardinal sin - it's even worse than double denim.

穿西装却不穿袜子简直“罪不可恕”——甚至比双牛仔还要糟糕。