As a Noun:
1. The act of causing a living thing to die. English = killing.
2. A person who has killed someone. English = killer.
3. Anything that causes death to a person, animal or plant. English = killer.
As a Verb or Adjective:
1. To cause a person, animal or plant to die. English = kill.
2. To kill a person in a violent way. Formal English = slay.