adj.腐烂变质的；谬误的；无根据的；靠不住的
In theory as well as in practice, the idea is unsound. 这个主意在理论上和实践上都站不住脚。
Do not listen to unsound advice. 别去听无根据的劝告。
I am afraid that it is an unsound investment. 我担心这项投资靠不住。
