Synonyms of unstable in English:

unstable


See US English definition of unstable

See UK English definition of unstable

See Spanish definition of inestable

adjective

1‘icebergs are notoriously unstable and may flip over’

SYNONYMS
unsteady, rocky, wobbly, wobbling, rickety, shaky, tottery, tottering, teetering, doddery, unsafe, unbalanced, unreliable, insecure, not secure, unfastened, unsecured, movable, precarious
Irish bockety
ANTONYMS

stable, steady

2‘the country suffered from unstable coffee prices’

SYNONYMS
changeable, volatile, variable, unsettled, fluctuating, inconstant, inconsistent, irregular, fitful, unpredictable, unreliable, fickle, capricious, mercurial, erratic, uncertain, wavering
informal peaky
ANTONYMS

stable, firm

3‘he was mentally unstable’

SYNONYMS
unbalanced, of unsound mind, mentally ill, deranged, demented, crazed, distracted, troubled, disturbed, unhinged, insane, mad, mad as a hatter, mad as a March hare, raving mad, lunatic, out of one's head, out of one's mind, not in one's right mind, neurotic, psychotic
non compos mentis
British sectionable
informal crazy, loopy, loony, mixed up, nuts, nutty, nutty as a fruitcake, bananas, cracked, crackpot, dippy, screwy, bats, cuckoo, bonkers, mental, screwed up, not all there, off one's head, out to lunch, a bit lacking, round the bend
British informal daft, barmy, crackers, barking, barking mad, batty, dotty, potty, off one's rocker, off one's trolley, daft as a brush, not the full shilling, round the twist, away with the fairies
North American informal nutsy, nutso, squirrelly, wacko, buggy
dated touched
ANTONYMS

stable, balanced