challenging

The definition of challenging is something that is difficult and intriguing.

(adjective)

An example of challenging is a tough research project about an interesting subject.

See challenging in American Heritage Dictionary 4

adjective

Calling for full use of one's abilities or resources in a difficult but stimulating effort: a challenging course of study; a challenging role for an inexperienced performer.
Absorbing; intriguing: a challenging idea.

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