toughen

1 ENTRIES FOUND:
toughen /ˈtʌfən/ verb
toughens; toughened; toughening
toughen
/ˈtʌfən/
verb
toughens; toughened; toughening
Britannica Dictionary definition of TOUGHEN
1 
: to make (something) stricter or to become stricter
[+ object]
— often + up
[no object]
— usually + up
2 
: to make (someone) physically or emotionally stronger or to become physically or emotionally stronger
[+ object]
— often + up
[no object]
— usually + up