1.  insecure(a = adj.all) - not firm or firmly fixed; likely to fail or give way; "the hinge is insecure"
Antonym: secure

2.  insecure(a = adj.all) unsafe - lacking in security or safety; "his fortune was increasingly insecure"; "an insecure future"
Antonym: secure
Derived forms noun insecureness₁, noun insecurity₁

3.  insecure(a = adj.all) - lacking self-confidence or assurance; "an insecure person lacking mental stability"
Antonym: secure
Derived forms noun insecureness₁, noun insecurity₂

4.  insecure(s = adj.all) unsafe - not safe from attack;
Derived forms noun insecureness₁, noun insecurity₁

1.  Not secure; not confident of safety or permanence; distrustful; suspicious; apprehensive of danger or loss. [1913 Webster]
"With sorrow and insecure apprehensions." [1913 Webster]

2.  Not effectually guarded, protected, or sustained; unsafe; unstable; exposed to danger or loss. Bp. Hurg. [1913 Webster]
"The trade with Egypt was exceedingly insecure and precarious." [1913 Webster]

insecure, adj.
1 (of a person or state of mind) uncertain; lacking confidence.
2 a unsafe; not firm or fixed. b (of ice, ground, etc.) liable to give way.

Derivative:
insecurely adv. insecurity n.

N  danger, peril, insecurity, jeopardy, risk, hazard, venture, precariousness, slipperiness, instability, defenselessness, exposure, vulnerability, vulnerable point, heel of Achilles, forlorn hope, leap in the dark, road to ruin, faciles descensus Averni, hairbreadth escape, cause for alarm, source of danger, rock ahead, breakers ahead, storm brewing, clouds in the horizon, clouds gathering, warning, alarm, apprehension, in danger, endangered, fraught with danger, dangerous, hazardous, perilous, parlous, periculous, unsafe, unprotected &c (safe, protect), insecure, untrustworthy, built upon, sand, on a sandy basis, wildcat, defenseless, fenceless, guardless, harborless, unshielded, vulnerable, expugnable, exposed, open to, aux abois, at bay, on the wrong side of the wall, on a lee shore, on the rocks, at stake, in question, precarious, critical, ticklish, slippery, slippy, hanging by a thread, with a halter round one's neck, between the hammer and the anvil, between Scylla and Charybdis, between a rock and a hard place, between the devil and the deep blue sea, between two fires, on the edge of a precipice, on the brink of a precipice, on the verge of a precipice, on the edge of a volcano, in the lion's den, on slippery ground, under fire, not out of the wood, unwarned, unadmonished, unadvised, unprepared, off one's guard, tottering, unstable, unsteady, shaky, top-heavy, tumbledown, ramshackle, crumbling, waterlogged, helpless, guideless, in a bad way, reduced to the last extremity, at the last extremity, trembling in the balance, nodding to its fall, threatening, ominous, illomened, alarming, explosive, adventurous, incidit in Scyllam qui vult vitare Charybdim, nam tua res agitur paries dum proximus ardet.

N  transience, transientness, evanescence, impermanence, fugacity, caducity, mortality, span, nine days' wonder, bubble, Mayfly, spurt, flash in the pan, temporary arrangement, interregnum, velocity, suddenness, changeableness, transient, transient boarder, transient guest, transient, transitory, transitive, passing, evanescent, fleeting, cursory, short-lived, ephemeral, flying, fugacious, fugitive, shifting, slippery, spasmodic, instantaneous, momentaneous, temporal, temporary, provisional, provisory, deciduous, perishable, mortal, precarious, unstable, insecure, impermanent, brief, quick, brisk, extemporaneous, summary, pressed for time, sudden, momentary, temporarily, pro tempore, for the moment, for a time, awhile, en passant, in transitu, in a short time, soon, briefly, at short notice, on the point of, on the eve of, in articulo, between cup and lip, one's days are numbered, the time is up, here today and gone tomorrow, non semper erit aestas, eheu! fugaces labuntur anni, sic transit gloria mundi, a schoolboy's tale, the wonder of the hour!, dum loquimur fugerit invidia aetas, fugit hora, all that is transitory is but an illusion.