unmarry
/(ˌ)ʌnˈmari/verb
1To render (a person or persons) unmarried; to dissolve the marriage of; to divorce. Also refl., and occasionally without object.
2To repudiate or divorce (a spouse); to reverse or undo marriage to (a partner).
3 [no object] To become unmarried; to dissolve one's marriage; to obtain a divorce.
Origin
Middle English (in an earlier sense). From un- + marry.