ironclad
1. Fixed; inflexible; unbreakable. But not playing ball in the house is one of Mom's ironclad rules! I think any lawyer will have a hard time getting you out of that contract—it's ironclad. The syllabus isn't ironclad, of course, but I certainly hope that we're able to cover all of these works this semester.
2. Unable to be contradicted. I didn't even know what to say in response to the ironclad argument made by the opposing counsel. This security footage is ironclad evidence that you were a part of the robbery! I thought my hypothesis was ironclad—and then my lab partner showed me where I'd gone wrong.
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