Formal word for warning or admonishing someone, often by a superior, school, workplace, or authority. As 訓戒する, it takes the person being admonished as the object.
The principal admonished the student who broke the school rules.
彼は会社から訓戒を受けた。
He received a warning from the company.
2
noun, noun or participle which takes 'suru', transitive verb
admonitory lesson; warning maxim; phrase teaching what not to do
Also refers to the content of an admonition: a lesson, saying, or phrase meant to warn someone against bad behavior. This use is somewhat written or formal.