1. 遇到，遭遇（问题、困难）
    If you encounter problems or difficulties, you experience them.

    e.g. Every day of our lives we encounter stresses of one kind or another...
           我们在每天的生活中会面临这样或那样的压力。
    e.g. Environmental problems they found in Poland were among the worst they encountered.
           他们在波兰发现的环境问题是他们遇到过的最严重的。

2. 偶遇;邂逅
    If you encounter someone, you meet them, usually unexpectedly.

    e.g. Did you encounter anyone in the building?...
           你在大楼里遇到谁了么？
    e.g. Renata wrote him that she had encountered her long-estranged father.
           雷娜塔写信告诉他说她碰到了分离多年的父亲。

3. 偶遇;邂逅;(重要的)相逢
    An encounter with someone is a meeting with them, particularly one that is unexpected or significant.

encounter

    e.g. The author tells of a remarkable encounter with a group of South Vietnamese soldiers.
           作者讲述了和一群南越士兵的奇遇。

4. 特殊经历;特殊体验
    An encounter is a particular type of experience.

    e.g. ...a sexual encounter.
           性体验
    e.g. ...his first serious encounter with alcohol.
           他第一次正儿八经喝酒的经历