1. 有身份的人；绅士
    A gentleman is a man who comes from a family of high social standing.

    e.g. ...this wonderful portrait of English gentleman Joseph Greenway.
           英国绅士约瑟夫·格林韦的精美画像

2. 有教养的人；彬彬有礼的人；君子
    If you say that a man is a gentleman, you mean he is polite and educated, and can be trusted.

    e.g. He was always such a gentleman.
           他总是那么彬彬有礼。

3. （对人礼貌的称呼）先生
    You can address men as gentlemen, or refer politely to them as gentlemen.

gentleman

    e.g. This way, please, ladies and gentlemen...
           女士们，先生们，这边请。
    e.g. It seems this gentleman was waiting for the doctor.
           这位先生好像在等医生。

4. （口头的）君子协定，绅士协定
    A gentleman's agreement or a gentlemen's agreement is an informal agreement in which people trust one another to do what they have promised. The agreement is not written down and does not have any legal force.

    e.g. We had no contract; it was done by a gentleman's agreement...
           我们没有签合同，就订了个君子协定。
    e.g. She made a gentleman's agreement with her buyer.
           她和买主立了个君子协定。