[mass noun] A common Eurasian pasture grass with soft downy leaves.
- ‘There is evidence that Yorkshire fog may have an allelopathic effect on other plants in the sward.’
- ‘It looks a bit like Yorkshire fog although it is quite early for it to be flowering.’
- ‘I also think they do not really like the Yorkshire fog very much at this time of year.’
Late 19th century: fog from fog.