1. 关系不大的;不直接相干的
If you describe something as tangential, you mean that it has only a slight or indirect connection with the thing you are concerned with, and is therefore not worth considering seriously.

2. 切线的;相切的
If something is tangential to something else, it is at a tangent to it.

1. of superficial relevance if any

e.g. a digressive allusion to the day of the week
a tangential remark

Synonym: digressive

2. of or relating to or acting along or in the direction of a tangent

e.g. tangential forces