WordNet sense 1 (tall Old World biennial thistle with large clasping white-blotched leaves and purple flower heads; naturalized in California and South America):

milk thistle, holy thistle, lady's thistle, Our Lady's mild thistle, Silybum marianum

WordNet sense 2 (annual of Mediterranean to Portugal having hairy stems and minutely spiny-toothed leaves and large heads of yellow flowers):

sweet sultan, Cnicus benedictus