rock-solid for learners of EnglishPowered by COBUILD also rock solid
Something that is rock-solid is extremely hard. ⇒ Freeze it only until firm but not rock solid.
If you describe someone or something as rock-solid, you approve of them because they are extremely reliable or unlikely to change. [approval] ⇒ Mayhew is a man of rock-solid integrity. ⇒ I'll need rock solid proof. ⇒ The firm is rock-solid financially. ⇒ The pound was rock solid at 2.88 Deutschmarks.