toughentough‧en /ˈtʌfən/ (also toughen up) verb [intransitive and transitive] Word Family: adverb: toughly, tough, toughly; verb: toughen; noun: toughness; adjective: toughto become tougher, or to make someone or something tougher: toughened glass Three years in the army toughened him up.
