blot your copybook
idiomPart ofblot
blot your copybook — idiom
1. to act in a way that makes other people think less well of you
1.idiom
Definition
to act in a way that makes other people think less well of you
Example
By lying about the test score, Ravi blotted his copybook at home.
The junior lawyer blotted her copybook by missing the judge's deadline.