1. a state of armed conflict between different nations or states or different groups within a nation or state
2. a sustained effort to deal with or end a particular undesirable situation or condition

1. to engage in or carry on warfare

Examples

• The two countries have been at war for three years.
• World War II ended in 1945.
• The government declared war on poverty.
• She has been waging war against corruption in the city.
• The neighboring tribes warred over territory.
• Veterans of the Vietnam War were honored at the ceremony.
• The war on drugs has been ongoing for decades.