harden/ 'hɒːdn /

1.vt.[+wax] [ glue etc] 
使变硬

2.vt.[+person] [ attitude] [ resolve] 
使变得冷酷无情

3.vi.[wax] [ glue etc+] 
变硬

4.vi.[person] [ attitude] [ resolve+] 
变得冷酷无情

to harden one's heart
使心肠变硬