1.
scrap, waste material
Small leftover pieces or fragments from something; materials no longer useful.
2.
worthless person (derogatory)
A derogatory term for a person considered to be useless or of low character.
屑 means scraps, waste, or refuse. It often appears in compounds referring to specific types of waste material.
Compounds
Insulting usage
When applied to people, 屑 is extremely derogatory — equivalent to calling someone "scum" or "trash." This usage is common in manga, anime, and online speech, but is very offensive in real life.
Writing
Often written in hiragana (くず) or katakana (クズ), especially in the insulting sense. The kanji 屑 appears more in formal or compound usage.