a dirty coward的用法和样例：
- My children think that work is a dirty word!
- It is dangerous to drive with a dirty windshield.
- They refused to go on a picnic on such a dirty day.
- He finds his wife has deserted him and with a dirty lowlife too.
- He wroth off a dirty kind of life by killing himself.
- I'm glad I don't have to go out on such a dirty night.