reprimand; stern warning
A formal, official warning or reprimand, often used in workplace, school, or legal contexts. Implies a serious, documented notice rather than a casual scolding.
He received a stern warning from his boss for repeated tardiness.
The police issued a stern warning to the violator.
注意 is a general warning or caution, while 厳重注意 is a much stronger, formal reprimand.
警告 is a warning, often with a threat of consequences; 厳重注意 is a severe reprimand that may or may not include explicit threats.
Compound of 厳重 (げんじゅう, 'strict, severe') and 注意 (ちゅうい, 'warning, caution').