rigorous

Characterized by or adhering to strict standards or methods; exacting and thorough.

Harsh, severe, or demanding.

Very unpleasant or inclement.

Adhering strictly to a belief or ideology; uncompromising or inflexible.

Acting with rigor; strict in performance or requirement.

Marked by inflexibility or severity; stringent; exacting; hence, unmitigated; merciless.

Exact; strict; precise; scrupulously accurate: as, a rigorous definition or demonstration.

Hard; inclement; bitter; severe: as, a rigorous winter.

Synonyms and Severe, Rigid, etc. (see austere), inflexible, unbending, unyielding.