Teasel n. : A plant of the genus Dipsacus, of which one species (D. fullonum) bears a large flower head covered with stiff, prickly, hooked bracts. This flower head, when dried, is used for raising a nap on woolen cloth.

Teasel n. : A bur of this plant.

Teasel n. : Any contrivance intended as a substitute for teasels in dressing cloth.

Teasel v. t. : To subject, as woolen cloth, to the action of teasels, or any substitute for them which has an effect to raise a nap.

Example:
My Q is when using the herb Teasel for treating lyme disease what part do I use the root or the leaf?

Taxonomy
Teasel, Dipsacus, teasels, Fuller's Teasel, Dipsacus fullonum, unranked, stem, free encyclopedia, leaves, Common Teasel, fabrics, genus name, Dipsacus laciniatus, invasive species, family Dipsacaceae, Dipsacus sativus, flower heads, cup.

Defination from the web:
teasel or teazel or teazle. ... Teasels are easily identified with their prickly stem and leaves, and the inflorescence of purple, dark pink or lavender flowers that form a head ...