Noun milk thistle has 2 senses
- sow thistle, milk thistle - any of several Old World coarse prickly-leaved shrubs and subshrubs having milky juice and yellow flowers; widely naturalized; often noxious weeds in cultivated soil
--1 is a kind of shrub, bush
--1 is a member of Sonchus, genus Sonchus
--1 has particulars: milkweed, Sonchus oleraceus
- milk thistle, lady's thistle, Our Lady's mild thistle, holy thistle, blessed thistle, Silybum marianum - tall Old World biennial thistle with large clasping white-blotched leaves and purple flower heads; naturalized in California and South America
--2 is a kind of herb, herbaceous plant
--2 is a member of Silybum, genus Silybum
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