Without proper thought; thoughtless. / Showing no regard; careless or unconcerned.

present participle of unthink

Incapable of being believed; incredible. / Inconceivable or unimaginable; extremely improbable in a way that goes against common sense.

In an unthinkable manner.

Third-person singular simple present indicative form of unthink

(transitive, intransitive) To undo the process of thinking.

The property of being unthinkable.

The property of being unthinkable.

plural of unthinker

One who does not think, or does not think wisely.