a.

1. 嚴格的；嚴厲的；苛刻的
   These soldiers have to undergo very rigorous trainings before they become frogmen.

   這些兵在成為蛙人之前都必須經過非常嚴峻的訓練。

2. 嚴酷的；嚴峻的
3. 精確的；嚴密的
   He made a rigorous study of the plants in the area.

   他對該地的植物進行了慎密的研究。

adj.

1. extremely thorough, exhaustive, or accurate.
2. (of a rule, system, etc.) strictly applied or adhered to.
   ▸adhering strictly to a belief or system.
3. harsh and demanding.