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.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.