Synonyms for Extreme:

adj.

abysmal (adjective)
profound.
agonizing (adjective)
violent.
all (adjective)
utmost, uttermost.
almighty (adjective)
awful.
deep (adjective)
grave.
different (adjective)
unusual.
edge (adjective)
border, boundary, brim, coastal, edge, fringe, marginal, peripheral, ringing, Rimming.
extreme (adjective)
absolute, acute, desperate, dire, drastic, exaggerated, excessive, extravagant, fabulous, fanatical, farthest, final, flagrant, furthermost, gross, highest, immoderate, improper, imprudent, inordinate, intemperate, intense, irrational, last, maximum, nonsensical, outermost, outmost, outrageous, overkill, preposterous, rabid, radical, remarkable, severe, sheer, strict, supreme, top, ultimate, unconventional, unreasonable, unusual, utmost, uttermost.
improper (adjective)
undue.
limiting (adjective)
bounding, confining, constraining, limiting, restricting, utmost, Restraining, Terminating, edge, maximum, zenith.
offensive (adjective)
outrageous.
overenthusiastic (adjective)
fanatical.
severe (adjective)
severe, almighty.
sharp (adjective)
sharp.
summit (adjective)
acme, apex, crowning, highest, maximum, peak, pinnacle, summit, tip, top, topmost, uppermost, zenith, Capping, Headmost, Culminating, loftiest.

adv.

farthest (adverb)
farthest, uttermost.

n.

exotic, farthest, final, last, notable, odd, offbeat, remarkable, special, surprising, ultimate, unique, unusual, out of the ordinary. absolute, absurd, abysmal, acute, advanced, almighty, big, cautious, childish, desperate, exaggerated, exorbitant, extravagant, extremist, fabulous, fanatical, fantastic, far, far-out, flagrant, gross, hysterical, immeasurable, improper, imprudent, inordinate, intemperate, irrational, irresponsible, moderate, monstrous, nonsensical, outrageous, overkill, overzealous, perverse, preposterous, profuse, rabid, restrained, ridiculous, sharp, sheer, steep, stiff, strict, super, ultra, unconventional, unmitigated, unqualified, unreasonable, violent, wrong, way out. awful, dire, farthermost, furthermost, furthest, grave, outermost, outmost, profound, rigorous, serious. apart, away, better, inaccessible, isolated, lonely, outlying, remote, supreme, transcendent, unsurpassable. aspect, component, excess, facet, factor, feature, nature, overabundant, overmuch, peculiarity, property, quality, undue. antithesis, balance, concern, fanatic, negation, obverse, opposite, opposition, pole, politics, revolutionary, the contrary, the converse, the reverse. extreme (noun)
acme, apex, boundary, distant, edge, excess, extreme point, extremum, immoderate, intense, peak, pinnacle, pole, utmost, uttermost, zenith.

Other synonyms:

absurd, childish, fantastic, far-out, gross, imprudent, irrational, irresponsible, nonsensical, outmost, overabundant, overmuch, perverse, rigorous, ultra, unsurpassable, wrong. dire, far, hysterical, outermost, profound, supreme, transcendent. acute, grave. awful, revolutionary. ultimate. fanatic. excessive
exorbitant, extravagant, intemperate.
fanatic
fanatical.
fanatical
rabid.
great
almighty.
immoderate
immoderate, inordinate, unreasonable.
intense
violent.
unconventional
way out.
Other relevant words:
absolute, absurd, abysmal, acute, advanced, almighty, antithesis, apart, aspect, away, awful, balance, better, big, cautious, childish, component, concern, desperate, dire, distant, drastic, exaggerated, excess, exorbitant, exotic, extravagant, extreme point, extremist, extremum, fabulous, facet, factor, fanatic, fanatical, fantastic, far, far-out, farthermost, farthest, feature, final, flagrant, furthermost, furthest, grave, gross, hysterical, immeasurable, immoderate, improper, imprudent, inaccessible, inordinate, intemperate, irrational, irresponsible, isolated, last, lonely, moderate, monstrous, nature, negation, nonsensical, notable, obverse, odd, offbeat, opposite, opposition, outermost, outlying, outmost, outrageous, overabundant, overkill, overmuch, overzealous, peculiarity, perverse, pole, politics, preposterous, profound, profuse, property, quality, rabid, remarkable, remote, restrained, revolutionary, ridiculous, rigorous, serious, sharp, sheer, special, steep, stiff, strict, super, supreme, surprising, transcendent, ultimate, ultra, unconventional, undue, unique, unmitigated, unqualified, unreasonable, unsurpassable, unusual, uttermost, violent, wrong, way out.

Usage examples for extreme

  1. I am putting extreme cases. – Frank H. Nelson of Cincinnati by Warren C. Herrick
  2. It is hard to form an idea of the extreme care with which this was done. – The Hunters of the Ozark by Edward S. Ellis
  3. In 1596 Burghley, in extreme old age, was a factor no longer to be taken into much consideration. – Raleigh by Edmund Gosse