腐(くさ)るto rot, to go bad, to decay, to spoil, to fester, to decompose, to turn sour (e.g. milk), to corrode, to weather, to crumble, to become useless, to blunt, to weaken (from lack of practice), to become depraved, to be degenerate, to be morally bankrupt, to be corrupt, to be depressed, to be dispirited, to feel discouraged, to feel down, indicates scorn or disdain for another's action, to lose a bet, to be drenched, to become sopping wet

腐(くさ)った遺体(いたい)から酷(ひど)いにおいがします。

There's a terrible smell coming from the decayed body.

凍傷(とうしょう)になったせいで足(あし)先(さき)が腐(くさ)ってしまいました。

My toes rotted due to frostbite.

こんな錆(さ)びて腐(くさ)ったナイフなんかで切(き)れるわけがない。

There's no way you can cut with such a rusty and blunted knife.

水槽(すいそう)の中(なか)の水(すい)が腐(くさ)らないように、定期(ていき)的(てき)に水(すい)を変(か)えています。

We change the water regularly to prevent it from going bad in the tank.

さすがあの監督(かんとく)だ。根性(こんじょう)が腐(くさ)っていると思(おも)われたやつも更生(こうせい)させた！

As expected of that coach. He even reformed those who were thought to be morally bankrupt!