to challenge; to take on a challenge; a challenge

She said she enjoyed the challenge.

Get ready to face the challenge!

But I will always be honest with you about the challenges we face. I will listen to you, especially when we disagree. And above all, I will ask you to join in the work of remaking this nation, the only way it's been done in America for 221 years; block by block, brick by brick, calloused hand by calloused hand.

That's a huge challenge.

And I know you didn't do this just to win an election. And I know you didn't do it for me. You did it because you understand the enormity of the task that lies ahead. For even as we celebrate tonight, we know the challenges that tomorrow will bring are the greatest of our lifetime: two wars, a planet in peril, the worst financial crisis in a century.