1. 二手的;用过的;旧的
Second-hand things are not new and have been owned by someone else.

e.g. Buying a second-hand car can be a risky business.
买二手车可能有风险。
e.g. ...a stack of second-hand books.
一摞旧书

2. 卖旧货的
A second-hand shop sells second-hand goods.

3. (故事、观点、信息)第二手的，间接的，非亲身经历的
Second-hand stories, information, or opinions are those you learn about from other people rather than directly or from your own experience.

e.g. He conceded that second-hand accounts are leading to rumour and counter-rumour...
他承认道听途说会引发谣言和辟谣。
e.g. The denunciation was made on the basis of second-hand information.
这些指责是依据二手信息提出的。

4. at second hand - see second