N. impossibility, what cannot, what can never be, sour grapes, hopelessness

V. be impossible, have no chance whatever, attempt impossibilities, square the circle, wash a blackamoor white, skin a flint, make a silk purse out of a sow's ear, make bricks without straw, have nothing to go upon, weave a rope of sand, build castles in the air, prendre la lune avec les dents, extract sunbeams from cucumbers, set the thames on fire, milk a he-goat into a sieve, catch a weasel asleep, rompre l'anguille au genou, be in two places at once

Adj. impossible, not possible, absurd, contrary to reason, unlikely, unreasonable, incredible, beyond the bounds of reason, beyond the bounds of possibility, beyond the realm of possibility, from which reason recoils, visionary, inconceivable, prodigious, unimaginable, inimaginable, unthinkable, impracticable unachievable, unfeasible, infeasible, insuperable, unsurmountable, insurmountable, unattainable, unobtainable, out of reach, out of the question, not to be had, not to be thought of, beyond control, desperate, incompatible, inaccessible, uncomeatable, impassable, impervious, innavigable, inextricable, self-contradictory, out of one's power, beyond one's power, beyond one's depth, beyond one's reach, beyond one's grasp, too much for, ultra crepidam

Phr. the grapes are sour, non possumus, non nostrum tantas componere lites, look for a needle in a haystack, chercher une aiguille dans une botte de foin, il a le mer boire