noun Date: 1837 a widely distributed weedy annual herb ( Polygonum persicaria ) of the buckwheat family that has large lanceolate leaves often with a blackish blotch suggesting a thumbprint
LADY'S THUMB
Meaning of LADY'S THUMB in English
Merriam Webster. Explanatory English dictionary Merriam Webster. Толковый словарь английского языка Мерриам-Уэбстер. 2012