firm, hard, rigid, steady, strong, resolute ☊ 
cứng cứng rắn kiên quyết 
stiff like: cứng rắn → →
unnachgiebig ☊ 
cứng rắn ☊ 
不让步的 ☊ bú ràngbù de unnachgiebig ☊ cứng rắn ☊ ☊ a big/nice/tough guy ☊ guy ☊
My joints are really stiff this morning. ☊ joint ☊
She's a tough lady. ☊ lady ☊
'Thank you,' she replied stiffly. ☊ stiffly ☊