Not likely to be true. / Not likely to happen.

The quality of being improbable.

The quality or state of being improbable; unlikelihood. / That which is improbable; an improbable event or result.

In an improbable manner; without probability.

plural of improbability

a lack of probity, honesty or integrity

(obsolete, transitive) To disapprove of. / (obsolete, transitive) To disallow.

plural of improbation

disapproval / (law, Scotland) The act by which falsehood and forgery are proved; an action brought for the purpose of having some instrument declared false or forged.

Implying, or tending to, improbation; disapproving.