Something that is unreliable and cannot be depended on for long, like a patron or support that will eventually fail; a shaky foundation or temporary backing.
他原本以为有位大人物做靠山，不料那位大人物很快失势，真是冰山易倒啊
He had thought he could rely on an influential figure, but unexpectedly that person soon lost influence. It truly shows that such support is like an iceberg easily collapsing.
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