noun
( plural heirs apparent )
Etymology: Middle English
1. : an heir whose right to an inheritance is indefeasible in law if he survives the legal ancestor
became heir apparent to the throne when his grandfather … was killed — Current Biography
2. : heir presumptive — not used technically
3. : one whose succession (as to a position or role) appears certain under existing circumstances
heir apparent to Mr. Churchill as prime minister — U.S. News & World Report
the Council of Europe, the parliamentary heir apparent of a federated Europe — J.R.Wike & A.Z.Rubinstein