Rock-steady is a term used to describe something that is firm, stable and unshakeable. Its antonyms are words that convey the opposite meaning such as unsteady, shaky, unstable, wobbly, faltering, uncertain, and unsure. These words describe things that lack stability, balance, and strength. An antonym for rock-steady also includes words such as fickle, wavering, and indecisive which describe the lack of consistency and reliability. A rock-steady person or thing is often seen as admirable and trustworthy, while the antonyms for rock-steady suggest weakness, frailty and an inability to withstand challenges.