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-adj)

Without humor or expression of happiness; grave in manner or disposition; earnest; thoughtful; solemn.

It was a surprise to see the captain, who had always seemed so serious , laugh so heartily.

Important; weighty; not trifling; leaving no room for play; needing great attention; critical.

This is a serious problem. We'll need our best experts.

Really intending what is said; being in earnest; not jesting or deceiving; meaningful.

After all these years, we're finally getting serious attention.