This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

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adj. Characterized by or acting with rigor: a rigorous program to restore physical fitness.

adj. Full of rigors; harsh: a rigorous climate.

adj. Rigidly accurate; precise. See Synonyms at burdensome.

adj. Manifesting, exercising, or favoring rigour; 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.

adj. Severe; intense; inclement; as, a rigorous winter.

adj. Violent.

adj. Manifesting, exercising, or favoring rigor; allowing no abatement or mitigation; scrupulously accurate; exact; strict; severe; relentless

adj. Severe; intense; inclement.

adj. Violent.

adj. Adhering scrupulously and exactly to accepted principles; hence, logically valid.

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.

adj. demanding strict attention to rules and procedures

adj. rigidly accurate; allowing no deviation from a standard

"CHENNAI: There is nothing rigorous about Mukunda Kumar€ ™ s prison stint though he was sentenced to €˜rigorous life imprisonment€ ™ four years ago."

demanding    exact   

austere    exact    stern    inflexible    rigid    unyielding    severe    strict    harsh    stiff   

vigorous   

strict    stringent    exact    systematic    mathematical    intensive    strenuous    arbitrary    ethical    scrupulous