What is the meaning of the word "war"?

Definitions:

a concerted campaign to end something that is injurious noun
- the war on poverty
a legal state created by a declaration of war and ended by official declaration during which the international rules of war apply noun
- war was declared in November but actual fighting did not begin until the following spring
an active struggle between competing entities noun
- a price war
the waging of armed conflict against an enemy noun
- thousands of people were killed in the war