IPA: /ˈmɜːrdərər/
KK: /ˈmɜrdərər/
A person who kills someone unlawfully and intentionally.
The police arrested the murderer after a long investigation.
Murderer → It is formed from "murder" (from Old English "morthor", meaning unlawful killing) and "-er" (meaning a person who). A murderer is a person who commits unlawful killing.
Think of someone who commits an unlawful killing ('murder') — the '-er' just means a person. This helps you remember that a murderer is someone who kills unlawfully.