What is the action of leaving something behind and no longer possessing it?

The action of leaving something behind and no longer possessing it is effectively captured by the word "abandoning." This term specifically conveys the idea of giving up control, possession, or support over something, often with an implication of neglect or a lack of intention to return.

"Retreating" refers more to moving back or withdrawing from a situation, often under pressure or danger, and does not necessarily involve the notion of leaving something permanently. Similarly, "departing" indicates simply leaving a place or situation but doesn't imply the abandonment of an object or responsibility. "Forsaking," while similar to abandoning, often carries a connotation of renouncing or rejecting something deliberately, usually involving an emotional or moral choice, which can add nuance that isn't strictly about possession. Thus, "abandoning" is the most accurate term to describe the act of leaving something behind without the intention of reclaiming it.