Advice, Caution
Noun, する verb, and の adjective
けいこく
借りた金を早く返すよう警告した。
I advised him that he should pay back money he borrowed soon.
あの選手はどの試合でも必ず警告のイエローカードを出されるね。
That player gets a yellow card warning in every game.
警告を無視するつもりなのか？
Do you intend to ignore this warning?
When you announce something to warn somebody, you're warning them. Sometimes you're just trying to give them some helpful advice.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.