sourdock
/ˈsɔrdɒk/Definitions
1. noun
A wild or weedy dock (Rumex spp.) with a sour-tasting leaf
“The hikers had to navigate through a field of sourdock on their way to the summit.”
2. verb
To eat or feed on dock or other wild plants, especially as a horse
“The pony began to sourdock on the green shoots of the newly planted garden.”