Collins Chinese Dictionary Plus (3rd edition), 2011:
不得已 bùdéyǐ 动
have no alternative but to
- 这(這)也是不得已而为(為)之的事情。 Zhè yě shì bùdéyǐ ér wéi zhī de shìqing. This is one of those things we have no alternative but to do.