Uncertain; unsafe; insecure.

That cannot be relied on to produce a particular result.

Not firm or steadfast; unreliable.

Faithless; unreliable.

Untrustworthy, not to be trusted (to), unreliable. Of things.

Marked or characterized by uncertainty or unsteadfastness; dependent on chance or accident; liable to fail; uncertain, precarious.

Of an observation, opinion, rule, argument, etc.: liable to be erroneous; that cannot be relied on with certainty.

Of conditions: On which one cannot depend; having no stability or certainty.

False, deceitful, treacherous. Obsolete.

Fickle, unreliable.

figurative. From which one may easily slip or fall; uncertain, mutable.

Subject to chance or accident; frail, uncertain, precarious. Obsolete.

Of conditions, affairs, etc.: Unstable, uncertain, insecure; that cannot be relied upon as lasting or assured. (Cf. 1b.)

= slippery, adj., in various literal and figurative senses.

Liable to fail or give way; unreliable.

Of uncertain issue.

= lubricous, adj., in various senses.

Affording no certainty. Obsolete. rare.

Of a matter or concern: uncertain, hazardous, tricky. Obsolete.

Not strengthened or fortified; not yet made firm or sure.

Critical, doubtful; full of risk or uncertainty. Obsolete.

Of the weather: changeable, unsettled; showery; (of rain showers) unpredictable. Also of a period of time: having unsettled weather. Cf. catchy, adj.…

Of conditions, undertakings, or engagements: Lacking security, unsettled. Obsolete.

= precarious, adj. 1.

Of an event, course of action, etc.: that has an uncertain outcome or conclusion; that could unfold in a number of different ways. Obsolete.

figurative. Of things: Deceptive, untrustworthy, unreliable; of ground, ice, etc., unstable, insecure.

Not to be trusted to; unreliable.

(un-, prefix1 affix 2.)

Esp. of a right, tenancy, etc.: held or enjoyed by the favour of and at the pleasure of another person; vulnerable to the will or decision of others…

figurative. Slippery, shifty; unsteady, unsettled; prone to danger or error. Obsolete.

Of uncertain issue or result.

figurative. ‘Slippery’, shifty; unstable; elusive.

Not established or firmly settled.

figurative. Unsettled, uncertain, undetermined; fluctuating, variable.

Const. of, or to with infinitive.

Not reliable; that cannot or should not be relied on.

Not tested or tried; (hence also) not reliable or trustworthy. Cf. unproved, adj. 1.

(un-, prefix1 affix 1.)

colloquial. Of questionable merit or prospects of success; uncertain, unreliable.

Wavering, uncertain, or insecure; unreliable, unstable.

slang (derogatory and now offensive). In southern African contexts: inferior or of a poor quality; inept, clumsy; contemptible, dishonest.

Not dependable; untrustworthy; not to be depended upon.

British colloquial. Of poor quality, unreliable; questionable, dubious.

Of a person: liable to peculiar moods, having or giving way to an erratic or neurotic temperament. Hence, of a thing: behaving erratically or…