n.

1. 事故；灾祸[C]
   He died in an automobile accident years ago.

   他数年前死于车祸。

2. 意外事情；偶然因素，机遇[C][U]
   The discovery was a happy accident.

   这一发现出人意料，令人高兴。

n.

1. an unfortunate incident that happens unexpectedly and unintentionally.
2. something that happens by chance or without apparent cause.
   ▸chance:

   we met by accident.
3. Philosophy  a property of a thing which is not essential to its nature.