The Collaborative International Dictionary
Lion's tail \Li"on's tail`\ (l[imac]"[u^]nz t[=a]l`) n. (Bot.) A genus of labiate plants ( Leonurus); -- so called from a fancied resemblance of its flower spikes to the tuft of a lion's tail. Leonurus Cardiaca is the common motherwort.
Motherwort \Moth"er*wort`\, n. (Bot.)
A labiate herb ( Leonurus Cardiaca), of a bitter taste, used popularly in medicine; lion's tail.
The mugwort. See Mugwort.
Wikipedia
Leonurus cardiaca, known as motherwort, is an herbaceous perennial plant in the mint family, Lamiaceae. Other common names include throw-wort, lion's ear, and lion's tail. Lion's tail also being a common name for Leonotis leonurus, and lion's ear, a common name for Leonotis nepetifolia. Originally from Central Asia and southeastern Europe, it is now found worldwide, spread largely due to its use as a herbal remedy.