rigorous

adj

1. strict, stringent, severe, stern, austere, spartan, harsh, rough, tough; rigid, hard, inflexible, unflexible, nonflexible, uncompromising; stiff, formal, structured; unbendable, unbending, unyielding, not giving an inch; inelastic, unplastic, non-pliant, unmalleable, nonmailable; fixed, set, firm, immovable, unalterable, unchangeable, unvarying, hard and fast, ironclad, absolute; undeviating, unswerving, persevering, unrelenting, relentless, implacable, inexorable; remorseless, pitiless, merciless, unsparing, unforgiving, hard-hearted, stony-hearted, cold-hearted; dominating, domineering, controlling, ironhanded, oppressive, repressive, despotic, tyrannical, autocratic, dictatorial.

2. exact, precise, accurate, literal, to the letter, nice, scientific, mathematical; exacting, demanding, close, painstaking, meticulous; difficult, arduous, strenuous, laborious, wearisome, exhausting, trying.

3.(all of weather or climate) inclement, bad, stormy, rain, windy; chilly, raw, bitter, biting, cold, nippy, freezing, frigid, arctic, icy, snowy, wintry.