unstable
un-sta-ble
adjective
Not firm or steady; likely to fall, collapse, or change suddenly.
"The wobbly table was quite unstable."
adjective
Prone to sudden, unpredictable changes in mood, behaviour, or condition.
"His mental state became increasingly unstable."
Thesaurus
Synonyms: irresolute, changeable, changeful, fluid, rocky, rickety, volatile, cranky, seismal, tipsy, coseismic, wobbly
Antonyms: stable