1. 做好准备;准备行动
If you are standing by, you are ready and waiting to provide help or to take action.
2. 坐视不理;袖手旁观
If you stand by and let something bad happen, you do not do anything to stop it.
3. 继续支持(尤指身处困境的人)
If you stand by someone, you continue to give them support, especially when they are in trouble.
4. 坚持，遵守，信守(原有的决定、承诺或宣言)
If you stand by an earlier decision, promise, or statement, you continue to support it or keep it.
1. be available or ready for a certain function or service
Synonym: stick aroundstick about
2. be loyal to
e.g. She stood by her husband in times of trouble
The friends stuck together through the war
3. not act or do anything
e.g. He just stood by when the police beat up the demonstrators