Adjective

(en adjective)

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.

*{{quote-magazine, date=2013-08-03, volume=408, issue=8847, magazine=(The Economist)

, title= Boundary problems , passage=Economics is a messy discipline: too fluid to be a science, too rigorous to be an art. Perhaps it is fitting that economists’ most-used metric, gross domestic product (GDP), is a tangle too. GDP measures the total value of output in an economic territory. Its apparent simplicity explains why it is scrutinised down to tenths of a percentage point every month.}}

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

Violent.

Adjective

(en adjective)

Urgent, ardent, zealous.

Requiring great exertion.

* 1961 : J. A. Philip. Mimesis in the ''Sophistês'' of Plato . In: Proceedings and Transactions of the American Philological Association 92. p. 467.

We can achieve this god?likeness only by unremitting and strenuous effort of the intellect.