a low European plant, Potentilla erecta, of the rose family, having small, bright-yellow flowers, and a strongly astringent root used in medicine and in tanning and dyeing.
tor·men·til (tôr'mən-tĭl') n. A perennial Eurasian plant (Potentilla erecta) having yellow flowers and astringent roots.
[Middle English tormentille, from Medieval Latin tormentilla, feminine diminutive of Latin tormentum, torment (from its use as an analgesic); see torment.]