cast-iron

1 of 1adjective

/ˈkæstˌaɪərn/

1

extremely robust

Synonyms:

2

not subject to change or doubt

There's no such thing as a cast-iron guarantee in politics.
She held a cast-iron belief in the value of hard work.
He followed a cast-iron routine every morning.
That contract is cast-iron; no room for negotiation.
The lawyer built a cast-iron case with solid evidence.