1. （难办或诱人的）事情，任务
    If you describe something such as a task or an activity as, for example, a difficult proposition or an attractive proposition, you mean that it is difficult or pleasant to do.

proposition的反义词

    e.g. Making easy money has always been an attractive proposition...
           轻松赚钱总是件诱人的事。
    e.g. Even among seasoned mountaineers Pinnacle Ridge is considered quite a tough proposition.
           即使在经验丰富的登山者中，平纳克尔峰也被认为是很难攀登的。

2. 见解；观点
    A proposition is a statement or an idea which people can consider or discuss to decide whether it is true.

    e.g. The proposition that democracies do not fight each other is based on a tiny historical sample.
           认为民主国家互不争斗的观点是以一个极小的历史样本为根据的。

3. （美国的）法律修正案
    In the United States, a proposition is a question or statement about an issue of public policy which appears on a voting paper so that people can vote for or against it.

    e.g. Vote Yes on Proposition 136, but No on Propositions 129, 133 and 134.
           对第136号修正案投赞成票，但对第129号、133号和134号修正案投反对票。

4. 提议；建议；提案
    A proposition is an offer or a suggestion that someone makes to you, usually concerning some work or business that you might be able to do together.

    e.g. You came to see me at my office the other day with a business proposition...
           几天前你带着一份商业提案来我的办公室见我。
    e.g. I want to make you a proposition.
           我想给你提一个建议。

5. 向…提出下流的要求；向…提出猥亵的要求
    If someone who you do not know very well propositions you, they suggest that you have sex with them.

    e.g. He had allegedly tried to proposition a colleague.
           据说他曾试图向一名同事求欢。