Definition of "difficult"

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

1850, Nathaniel Hawthorne, chapter 17, in The Scarlet Letter, a Romance, Boston, Mass.: Ticknor, Reed, and Fields

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.

2008, Daniel Goleman, Destructive Emotions: A Scientific Dialogue with the Dalai Lama, page 199

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. […] But as a foundation for analysis it is highly subjective: it rests on difficult decisions about what counts as a territory, what counts as output and how to value it. Indeed, economists are still tweaking it.

2013 August 3, “Boundary problems”, in The Economist, volume 408, number 8847

“I hope, madam,” said Jones, “my charming Lady Bellaston will be as difficult to believe anything against one who is so sensible of the many obligations she hath conferred upon him.”

1749, Henry Fielding, The History of Tom Jones, a Foundling

their Excellencies having desisted from their pretensions , which had difficulted the peace

August 9 1678, William Temple, letter to Joseph Williamson