To stand by as a spectator; to look on unconcerned; to remain aloof.
看到同事们为项目加班加点，他却选择凭轼旁观，没有伸出援手
Seeing his colleagues working overtime for the project, he chose to stand by and watch, offering no help.
Next Idiom
To stand by as a spectator; to look on unconcerned; to remain aloof.