- 1[transitive, intransitive] toughen (something) (up) to become or make something stronger, so that it is not easily cut, broken, etc. toughened glass
- 2[transitive] toughen something (up) to make something such as laws or rules stricter The government is considering toughening up the law on censorship.
- 3[transitive] toughen somebody (up) to make someone stronger and more able to deal with difficult situations His parents sent him away to school to toughen him up.
NAmE//ˈtʌfn//Verb Forms present simple I / you / we / they toughen
he / she / it toughens
past simple toughened
-ing form toughening