unstable

US /ʌnˈsteɪ.bəl/
UK /ʌnˈsteɪ.bəl/
"unstable" picture
1.

likely to change or give way; not stable

:
•
The old bridge is structurally unstable.
•
The political situation in the region remains highly unstable.
:
unsteadyprecariousshakywobblyvolatile
:
stablesteadyfirmsecurefixed
2.

prone to erratic or unpredictable changes of mood or behavior

:
•
He's been very unstable since the divorce.
•
Her emotions are quite unstable, swinging from joy to sadness quickly.
:
erraticficklemercurialunpredictablevolatile
:
calmcomposedsteadybalancedpredictable