also: のこりかす
noun
Refers to the leftover, often worthless or unwanted part after the main part has been used or taken away. Can be used for physical scraps, sediment, or figurative remnants.
コーヒーの残りカスを捨ててください。
Please throw away the coffee grounds.
議論の後には、いつも感情的な残りカスが残る。
After the argument, there are always emotional remnants left over.
Compound of 残り (nokori, 'remainder') and カス (kasu, 'dregs'). The katakana spelling of カス is common for this word.