Definition of milk thistle
: a tall thistle (Silybum marianum) having white-veined dark green leaves and large purple flower heads that is native to the Mediterranean region but has become naturalized elsewhere including the U.S.; also : an extract of milk thistle and especially its seeds that is held to protect the liver from damage or disease
First Known Use of milk thistle
Medical Definition of milk thistle
1: a tall thistle (Silybum marianum) that is the source of silymarin, has large clasping white-blotched leaves and large purple flower heads with bristly receptacles, and is native to southern Europe but has been widely introduced elsewhere including the United States
2: an extract of milk thistle and especially its seeds : silymarin
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