From Longman Dictionary of Contemporary Englishwarn off phrasal verb1 THREATEN warn somebody ↔ off to tell people that they should not go near something, especially because it might be dangerous Some animals mark their territory to warn off rivals.2 WARN warn somebody off (doing) something especially British English to tell someone that they should not do or use something because it might be dangerous Doctors should have warned people off using the drug much earlier than they did. → warn→ See Verb table
