Originally in military sense of intentionally cutting off one's own retreat (burning a bridge one has crossed) to commit oneself to a course of action, later used primarily to mean “alienate former friends”.
Even if you are dismissed from a job in the worst way, take care to not burn your bridges with unseemly comments on the way out, since you never know who you will meet again.
Mandarin: 過河拆橋／过河拆桥(zh)(guòhéchāiqiáo), 过河拆桥(zh)(guò hé chāi qiáo)(cross the river, tear down the bridge), 破釜沉舟(zh)(pòfǔchénzhōu)(smash the (cooking) pots and sink the boats)