TOEFL IELTS harmful Definition Causing or likely to cause damage or injury. Example "Smoking is harmful to your health and can lead to lung disease." Sign in to save TOEFL Quiz → IELTS Quiz → ← hardy harmless → Study tips featuring "harmful" Audit Your Own Writing to Find Gaps TOEFL Academic Vocabulary: Study by Topic Boost Your IELTS Writing With Precise Vocabulary Related words TOEFL swiftness GRE abash GRE abate GRE abbreviate GRE abbreviation SAT abdicate GRE abduct SAT abet GRE abhor GRE abide SAT abject TOEFL ablaze