unstable adj.
1 likely to change suddenly
VERBS appear, be, seem | become | remain | make sth, render sth Prison order is rendered unstable by young inmates serving short sentences.
ADV. extremely, highly, very | increasingly | rather, relatively, somewhat | basically, inherently | notoriously The building trade is notoriously unstable. | economically, politically a politically unstable region
2 not mentally normal
VERBS be, seem | become
ADV. highly, very | rather | emotionally, mentally vulnerable, emotionally unstable individuals
3 likely to move or fall
VERBS be, feel, look, seem | become, get The building was beginning to get unstable. | make sth
ADV. dangerously, extremely, very The wall was dangerously unstable. | rather, slightly
You can also check other dicts: unstable (English, 中文解释 ), wordnet sense, Collins Definition