7 toughen

toughen
v[I, Ip, Tn, Tn.p]
~ (sth/sb) (up) (cause sth/sb to) become tough or tougher (使某事物[某人])(更)坚韧, 坚强, 强硬
    The law needs toughening (up). 需要加强法制的威力.
    toughened glass 钢化玻璃.