1. 障碍物
    An obstacle is an object that makes it difficult for you to go where you want to go, because it is in your way.

obstacle的解释

    e.g. Most competition cars will only roll over if they hit an obstacle...
           大多数赛车只有在撞上障碍物时才会翻车。
    e.g. He left her to navigate her own way round the trolleys and other obstacles.
           他扔下她一个人在一堆手推车和其他障碍物之间绕来绕去。

2. 障碍；困难；阻碍
    You can refer to anything that makes it difficult for you to do something as an obstacle .

    e.g. Overcrowding remains a large obstacle to improving conditions...
           过分拥挤仍然是改善环境的一大障碍。
    e.g. To succeed, you must learn to overcome obstacles.
           必须学会克服困难才能成功。