A Stink Spirit is, apparently, a spirit so disgusting that it appears as a large, smelly mass of sludge or ooze. One such Stink Spirit appeared in Spirited Away.
However, the Stink Spirit that appeared was actually just a River Spirit that had been too polluted by garbage that needed to be removed. His smell is so unbearable that even food becomes bad, rotting when he passes by, without touching it.
- It appears that regular spirits can become Stink Spirits when they are heavily contaminated by human garbage and pollutants.