formidable ·adjective (DIFFICULT)
Definition: difficult and needing a lot of effort or thought Level: C2
在没有额外帮助的情况下按时完成这个项目是一项艰巨的任务。
Completing the project on time was ___formidable without additional help.
面对学习一门新语言这项艰巨的任务，她一开始感到不知所措。
Faced with the ___formidable task of learning a new language, she felt initially overwhelmed.
克服如此巨大的障碍需要极大的毅力和创新思维。
Overcoming such a ___formidable obstacle required immense perseverance and innovative thinking.