/ ˈhɑːdn; NAmE ˈhɑːrdn/ verb
1.
to become or make sth become firm, stiff or solid :
[ v ]
The varnish takes a few hours to harden.
[ vn ]
a method for hardening and preserving wood
2.
if your voice, face, etc. hardens , or you harden it, it becomes more serious or severe :
[ v ]
Her face hardened into an expression of hatred.
[ vn ]
He hardened his voice when he saw she wasn't listening.
3.
if sb's feelings or attitudes harden or sb/sth hardens them, they become more fixed and determined :
[ v ]
Public attitudes to the strike have hardened.
Their suspicions hardened into certainty.
[ vn ]
The incident hardened her resolve to leave the company.
4.
[ vn ] [ usually passive ] to make sb less kind or less affected by extreme situations :
Joe sounded different, hardened by the war.
They were hardened criminals (= they showed no regret for their crimes) .
In this job you have to harden your heart to pain and suffering.
► hard·en·ing noun [ U , sing. ]:
hardening of the arteries
a hardening of attitudes towards one-parent families