1. (

• challenge ,
• dispute ,
• gainsay

) take exception to; "She challenged his claims" ;

2. (

• challenge

) issue a challenge to; "Fischer challenged Spassky to a match" ;

3. (

• challenge ,

) ask for identification; "The illegal immigrant was challenged by the border guard" ;

4. (

• challenge ,
• take_exception ,

) raise a formal objection in a court of law ;

1. (

• ambitious ,
• challenging

) requiring full use of your abilities or resources; "ambitious schedule"; "performed the most challenging task without a mistake" ;

2. (

• challenging ,
• thought-provoking

) stimulating interest or thought; "a challenging hypothesis"; "a thought-provoking book" ;

3. (

• challenging ,
• intriguing

) disturbingly provocative; "an intriguing smile" ;