1. one long cylindrical thing; one film, TV show, etc.; one goal, home run, etc.; one telephone call
もはや指一本動かせない。I can no longer move even a single finger.
2. one version
3. one book; a certain book
4. ippon; one point; a blow
5. geisha
6. single-minded focus on ...
after a noun; usu. as ...～で, ...～に, etc.
父は仕事一本の人だった。My father was a man who lived only for his work.