The old man lost all his savings in a bunco disguised as an investment opportunity.

bunco 是美国俚语，指"骗局、欺诈行为"，源自西班牙语"banca"（赌博骗局）。这个词特指精心设计的诈骗圈套，常通过虚假承诺诱骗受害者钱财。