challenge
invitation to measure oneself against others, to confront them in a competition
Copenhagen Climate Challenge
was organised by the Committee for a Constructive Tomorrow
DARPA Grand Challenge
driverless car competition held in 2004
inducement prize contest
competition that awards a prize as incentive for accomplishing a pre-specified feat (e.g. engineering)
Ocean's seven
The Oceans Seven is a marathon swimming challenge
Condom challenge
two viral Internet challenges
Internet challenge
popular phenomenon on the Internet
Cinnamon challenge
Internet challenge
Three Poles Challenge
adventure challenge to reach the North Pole, the South Pole, and the summit of Mount Everest
challenge
act of challenging the validity of a word played in the game of Scrabble
Virgin Earth Challenge
competition
Bottle Cap Challenge
viral challenge involving kicking the cap off a bottle
hackathon
event in which groups of software developers work at an accelerated pace
No Nut November
annual internet challenge of male sexual abstinence during November
choking game
dangerous game of trying to faint
challenge
request made to the holder of a competitive title for a match between champion and challenger
One Chip Challenge
spicy snack Internet challenge
Bonn Challenge
global effort to restore the world's degraded and deforested lands