This is the 7752nd most frequent Japanese word.
古式
"Ancient style" or "traditional style."
The word 古式 refers to ancient or traditional styles or ways, used to describe the traditional method the festivals follow.
この神社では古式に則った祭りが行われます。
At this shrine, festivals are held in accordance with ancient traditions.
Here, 古式 describes the tea ceremony as elegant and traditional, emphasizing the historical aspect.
古式ゆかしい茶道の作法を学びました。
I learned the etiquettes of the refined traditional tea ceremony.
In this sentence, 古式 is used to characterize the martial arts as stemming from ancient times, preserving their original methods.