Small pieces of trash or refuse; worthless rubbish. Can also be used contemptuously to refer to something of no value.
毎朝、ごみくずを分別して出しています。
Every morning I sort and put out the trash.
床にごみくずが落ちているから、掃除しておいてください。
There are bits of trash on the floor, so please clean them up.
そんなことで自分を責めるなんて、自分をごみくず扱いしないで。
Don't treat yourself like trash for something like that.