rigorous

adj. harsh, strict, severe; exact, precise, strictly accurate

For the medical term see rigor (medicine) Rigour or rigor (see spelling differences) has a number of meanings in relation to intellectual life and discourse. These are separate from judicial and political applications with their suggestion of laws enforced to the letter, or political absolutism. A religion, too, may be worn lightly, or applied with rigour.
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Adjective
1. rigidly accurate; allowing no deviation from a standard; "rigorous application of the law"; "a strict vegetarian"
(synonym) strict
(similar) exact
2. demanding strict attention to rules and procedures; "rigorous discipline"; "tight security"; "stringent safety measures"
(synonym) stringent, tight
(similar) demanding
3. used of circumstances (especially weather) that cause suffering; "brutal weather"; "northern winters can be cruel"; "a cruel world"; "a harsh climate"; "a rigorous climate"; "unkind winters"
(synonym) brutal, cruel, harsh, unkind
(similar) hard

(a.)
Violent.
  

(a.)
Severe; intense; inclement; as, a rigorous winter.
  

(a.)
Manifesting, exercising, or favoring rigor; allowing no abatement or mitigation; scrupulously accurate; exact; strict; severe; relentless; as, a rigorous officer of justice; a rigorous execution of law; a rigorous definition or demonstration.
  

Synonyms and 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