Wiktionary
adv. In an unthinkable manner.
WordNet
adv. to an unimaginable extent [syn: unimaginably]
Usage examples of "unthinkably".
As yet, his case hadn't been heard on Atria XVI, for on that unthinkably frigid world there were no bills of indictment, no pretrial hearings, nothing but a simple verdict of innocent or guilty.
Ward, dazed by the flood of grotesque morbidities and unthinkably maddening suggestions that poured in upon him from every side, could only acquiesce.
Upon the unthinkably explosive object they would no doubt paint, Amalfi surmised, had they by that time also composed an anti-material paint and something to keep it in, the warning Noli me tangere.
The butcher's bill would be unthinkably high for any attempt at placing petards, and in order for his six minions to accomplish anything at all, they would have to go into battery virtually under the looming mouths of some dozen demiculverins cunningly emplaced on the side of the hill that arose hard by the left side of the road.
The galaxy is unthinkably huge, and we are, after all, still essentially in Earth's own backyard, bouncing around a sphere no more than a hundred light-years in diameter, out here in one small arm of the galaxy, 30,000 light-years from the center.