noun挑战,艰巨任务;挑战书,参赛邀请
verb拒绝接受,提出质疑;挑战;发出挑战
nouna new or difficult thing that makes you try hard
nounan invitation to fight or play a game against somebody
verbto refuse to accept a set of rules; to say that you think somebody or something is wrong
verbto ask somebody to play a game with you or fight with you to see who wins