lengthen
verbNAmE//ˈlɛŋkθən//, NAmE//ˈlɛŋθən//
[intransitive, transitive]Verb Forms present simple I / you / we / they lengthen he / she / it lengthens
past simple lengthened
-ing form lengthening
Check pronunciation: lengthen
Definition of lengthen verb from the Oxford Advanced American Dictionary