Challenging

['tʃælɪn(d)ʒɪŋ] or ['tʃælɪndʒɪŋ]

(adj.) disturbingly provocative; 'an intriguing smile' .

(adj.) stimulating interest or thought; 'a challenging hypothesis'; 'a thought-provoking book' .

Checked by Clarice--From WordNet

(p. pr. & vb. n.) of Challenge

Inputed by Estella