challenging as in requiring full use of your abilities or resources

• "ambitious schedule"
• "performed the most challenging task without a mistake"

Synonyms

• ambitioushaving a strong desire for success or achievement ; requiring full use of your abilities or resources

challenging as in stimulating interest or thought

• "a challenging hypothesis"
• "a thought-provoking book"

Synonyms

• thought-provokingstimulating interest or thought

challenging as in disturbingly provocative

• "an intriguing smile"

Synonyms

• intriguingdisturbingly provocative; capable of arousing interest or curiosity