challenging

• POS: Adjective
• HYPHEN: chal=leng=ing

CIDE DICTIONARY

challenging, adj. 

•  requiring full use of one's abilities or resources; as, challenging task.  [WordNet 1.5]
•  disposed to or engaged in defiance of established authority.  [WordNet 1.5]

THESAURUS

challenging

alluring, arrogant, audacious, bold, brash, brassy, brazen, bumptious, cheeky, cocky, contemptuous, daring, defiant, defying, derisive, disdainful, disregardful, encouraging, energizing, exciting, galvanic, galvanizing, greatly daring, impertinent, impudent, insolent, inviting, pert, piquant, prompting, provocative, provoking, regardless of consequences, rousing, saucy, stimulant, stimulating, stimulative, stirring