a relationship in which people agree to work together; 2 : the state of being joined in some activity or effort the state of being allied Alliance Lifetime Mental Health Inc. How to use alliance in a sentence. 5 days ago ยท Browse Alliance local obituaries on Legacy. ALLIANCE definition: 1. ALLIANCE meaning: 1 : a union between people, groups, countries, etc. The meaning of ALLIANCE is the state of being allied : the action of allying. Honor and remember your loved ones in Alliance, OH. Countries that have an alliance, or agreement, help each other out when in need. a group of countries, political parties, or people who have agreed to work together because of…. Find contact information, view maps, and more.