| melancholy thistle | (n) perennial stoloniferous thistle of northern Europe with lanceolate basal leaves and usually solitary heads of reddish-purple flowers, Syn. Cirsium helenioides, Cirsium heterophylum |
| milk thistle | (n) tall Old World biennial thistle with large clasping white-blotched leaves and purple flower heads; naturalized in California and South America, Syn. Our Lady's mild thistle, Silybum marianum, blessed thistle, holy thistle, lady's thistle |