List of rigorous synonyms and rigorous related words.
Herculean, Siberian, abstruse, accurate, acid, acidulous, acrid, acrimonious, acute, adamant, adamantine, adverse, algid, antagonistic, arctic, arduous, ascetic, astringent, attentive, below zero, biting, bitter, bitterly cold, bleak, boreal, brisk, brumal, brutal, burdensome, cast-iron, caustic, close, cold, cold as charity, cold as death, cold as ice, cold as marble, complex, conflicting, conscientious, constant, contrary, correct, counter, counteractive, crisp, critical, cutting, delicate, demanding, detailed, detrimental, difficile, difficult, direct, double-edged, dour, draconian, drastic, edged, escharotic, even, exact, exacting, excessive, exigent, exorbitant, express, exquisite, extravagant, extreme, faithful, fierce, fine, finical, finicking, finicky, firm, flinty, formidable, freezing, freezing cold, frigid, fundamentalist, furious, fussy, gelid, glacial, great, grim, hairy, hard, hard-core, hard-earned, hard-fought, harmful, harsh, hibernal, hidebound, hiemal, hostile, hyperborean, ice-cold, ice-encrusted, icelike, icy, immoderate, immovable, immutable, implacable, impliable, in opposition, incisive, inclement, inelastic, inerrable, inerrant, inexorable, infallible, inflexible, inimical, intemperate, intense, intransigent, intricate, iron, ironbound, ironclad, ironhanded, irreconcilable, jawbreaking, keen, knotted, knotty, laborious, mathematical, mean, meticulous, micrometrically precise, microscopic, minute, miserable, mordacious, mordant, muscle-bound, narrow, nice, nipping, nippy, no picnic, not easy, numbing, obdurate, obstinate, onerous, operose, opposed, opposing, opposite, oppressive, orthodox, outrageous, particular, penetrating, piercing, pinching, pinpoint, poignant, precise, precisianistic, precisionistic, procrustean, proper, punctilious, punctual, purist, puristic, puritan, puritanic, raw, refined, relentless, religious, religiously exact, right, rigid, rigorist, rigoristic, rock-ribbed, rockbound, rough, rugged, scathing, scientific, scientifically exact, scrupulous, scrutinizing, set with thorns, severe, sharp, sinister, sleety, slushy, snappy, spiny, splitting, square, stabbing, steely, steep, stern, stiff, stinging, stone-cold, straightlaced, straitlaced, strenuous, stressful, strict, strident, stringent, stubborn, subtle, subzero, supercooled, tart, thorny, ticklish, toilsome, tough, trenchant, tricky, troublesome, troublous, trying, unaffected, unalterable, unbending, unchangeable, uncompromising, unconscionable, undeviating, unerring, unfavorable, ungiving, unmoved, unrelenting, untoward, unyielding, uphill, vehement, venomous, violent, virulent, vitriolic, wicked, winterbound, winterlike, wintery, wintry, wretched