Home › Words › I › instrengtheninstrengthen/ɪnˈstɹɛŋθə̆n/instrengthen means strengthen inwardly.instrengthen is pronounced /ɪnˈstɹɛŋθə̆n/.EtymologyFrom in- + strengthen; compare enstrengthen.verbStrengthen inwardly.Definitions & examples from Wiktionary (CC BY-SA 3.0).