What is "counter-enlightenment"

The Counter-Enlightenment was a term that some 20th-century commentators have used to describe multiple strains of thought that arose in the late-18th and early-19th centuries in opposition to the 18th-century Enlightenment. The term is usually associated with Isaiah Berlin, who is often credited with coining it, perhaps taking up a passing remark of the German philosopher Friedrich Nietzsche, who used the term Gegenaufklärung at the end of the 19th century. The first known use of the term 'counter-enlightenment' in English was in 1949. Berlin published widely about the Enlightenment and its enemies and did much to popularise the concept of a Counter-Enlightenment movement that he characterised as relativist, anti-rationalist, vitalist, and organic, and which he associated most closely with German Romanticism.