TOEFL IELTS lengthen Definition To make or become longer in duration or physical size. Example "As summer approaches, the days begin to lengthen." Sign in to save TOEFL PDF — $25 IELTS PDF — $25 ← leisurely lengthy → Study tips featuring "lengthen" TOEFL Academic Vocabulary: Study by Topic Boost Your IELTS Writing With Precise Vocabulary Related words TOEFL brighten GRE abash GRE abate GRE abbreviate GRE abbreviation SAT abdicate GRE abduct SAT abet GRE abhor GRE abide SAT abject TOEFL ablaze