Adjective

(er)

In shadow; darkened by shadows.

He sat in a shadowy corner.

(of character) Dark, obscure.

He was a shadowy man who rarely spoke.

* {{quote-news

, year=2011 , date=December 19 , author=Kerry Brown , title=Kim Jong-il obituary , work=The Guardian citation , page= , passage=By 1980, South Korea had overtaken its northern neighbour, and was well on its way to being one of the Asian tigers – high-performing economies, with democratic movements ultimately winning power in the 1990s. The withdrawal of most Soviet aid in 1991, with the fall of the Soviet empire, pushed North Korea further down. Kim Il-sung had held a genuine place on North Korean people's affections. His son was regarded as a shadowy playboy, with rumours circulating over the years that he imported Russian and Chinese prostitutes, and lived a life of profligacy and excess.}}

Adjective

(en adjective)

Hard, not easy, requiring much effort.

* (Nathaniel Hawthorne) (1804-1864)

There is not the strength or courage left me to venture into the wide, strange, and difficult world, alone.

* 2008 , Daniel Goleman, Destructive Emotions: A Scientific Dialogue with the Dalai Lama (ISBN 0307483762), page 199:

In adults, the same kind of anger has been studied in people trying to solve a very difficult math problem. Though the tough math problem is very frustrating, there is an active attempt to solve the problem and meet the goal.

* {{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.

Hard to manage, uncooperative, troublesome.