"Unstable" means not being steady, secure, or predictable. It implies a lack of balance or firmness, leading to changes or uncertainties that can make something or someone unreliable or unsafe. Full definition
This could mean that the balance aspect of unstable surface training could lead to strength gains irrespective of the loading used. (strengthandconditioningresearch.com)
With league finishes of 7th, 4th and 5th, and 3 managers later, the club has become unstable with much lower and inconsistent league results. (bigfreebet.com)
Soon, everyone from the man's wife to his co-workers and mentally unstable sister becomes a suspect. (bookpage.com)