1. 铸铁;生铁
Cast iron is iron which contains a small amount of carbon. It is hard and cannot be bent so it has to be made into objects by casting.

2. (保证或借口)可靠的，可信的，无懈可击的
A cast-iron guarantee or alibi is one that is absolutely certain to be effective and will not fail you.

1. an alloy of iron containing so much carbon that it is brittle and so cannot be wrought but must be shaped by casting