Meaning of UNSTABLE in English
[adjective] - not solid and firm and therefore not strong, safe or likely to lastI don't think you ought to let anybody sit in that chair - it looks a bit unstable to me.It is a poor and politically unstable society in which warlords wield more power than the government.The future of the world's second largest auctioneer looks increasingly unstable this week.A person might be described as unstable if they suffer from sudden and extreme changes in their mental and emotional state.I would describe her as emotionally unstable.
Cambridge English vocab. Кембриджский английский словарь. 2012