Answer: rocksolid

AnswerCrossword Clue
ROCKSOLIDUnshakable
ROCKSOLIDDependable to the max
ROCKSOLIDDependable beyond doubt
ROCKSOLIDReliable
ROCKSOLIDStaunch
ROCKSOLIDHighly unlikely to change
ROCKSOLIDAbsolutely dependable
ROCKSOLIDWatertight
ROCKSOLIDThe stonemason's alibi was ..