success in doing something well, usually by working hard: Graduating from college was my greatest _________.
achievement
something that is difficult and that tests someone’s ability: I recently ran 30 miles across a mountain trail. I wasn't sure I could do it; I had to train very hard. It was a real ______________
Challenge
a piece of work that you have to do: We're organizing our garage this weekend. It's going to be a big _____________.
job