“+ adjective
Etymology: Middle English, from un- (I) + stable
: not stable: as
a.
(1) : not firm or fixed in one place : apt to move : movable
snow as unstable as aspic trembled on the steep slope — R.L.Neuberger
the unstable shifting sands of the desert
(2) : lacking steadiness : apt to sway or fall
the tower proved to be unstable in a high wind
the bird flutters on its unstable pech
(3) : not steady in movement : irregular
felt the unstable tripping beat of her heart
(4) : not firm or substantial : weak , insecure
the young earth was yet unstable , the molten forces within were constantly looking for escape — W.E.Swinton
the road may become so unstable as to compel the imposition of a speed limit — O.S.Nock
built on an unstable foundation
b.
(1) : wavering in purpose or intent : vacillating
an unstable and uneasy class of yeomen — S.E.Morison & H.S.Commager
his rather unstable religious convictions — H.E.Starr
woman's love … is volatile, insoluble, unstable — Marcia Anderson
(2) : exhibiting or characterized by emotional instability
an unstable temperament — Rex Ingamells
the unstable prisoners … placed in the vague but convenient category of psychopaths — A.H.MacCormick
had brought an inherently unstable nature to the point of mental and emotional collapse — E.J.Simmons
c.
(1) : variable in character or condition : liable to change or alteration : changeable
an unstable world economy … subjected to periods of wars, inflation, and depression — Farmer's Weekly (South Africa)
the wind might change; for it is an unstable world — Charles Kingsley
unstable climate
unstable relationship
(2) : readily decomposing or changing otherwise in chemical composition or biological activity — compare labile 3, sensitive 4e
(3) : readily changing in physical state or properties
unstable emulsions tend to separate into layers
(4) : spontaneously radioactive
Synonyms: see inconstant