a cast-iron excuse/alibi/guarantee etcEFFECTIVEan excuse etc that is very certain and cannot fail 理由充分的借口/不在犯罪现场的铁证/强有力的保证等a cast-iron excuse/alibi/guarantee etc• According to Ken Harris, she has a cast-iron alibi.• Do not expect a cast-iron guarantee of success.
→ a cast-iron excuse/alibi/guarantee etc at cast-iron(1)