THISTLE, n. this'l. The common name of numerous prickly plants of the class Syngenesia, and several genera; as the common corn thistle, or Canada thistle, of the genus Serratula or Cnicus; the spear thistle of the genus Cnicus; the milk thistle of the genus Carduus; the blessed thistle of the genus Centaurea; the globe thistle of the genus Echinops; the cotton thistle of the genus Onopordon; and the sow thistle of the genus Sonchus. The name is also given to other prickly plants not of the class Syngenesia; as the fuller's thistle or teasel of the genus Dipsacus, and the melon thistle and torch thistle of the genus Cactus.

One species of thistle, (Cnicus arvensis,) grows in fields among grain, and is extremely troublesome to farmers. It is called in America the Canada thistle, as it first appeared in Canada, where it was probably introduced from France, as it abounds in Normandy, and also in England. A larger species in America (Cnicus lanceolatus,) is indigenous, but it spreads slowly and gives no trouble.

Thorns also and thistles shall it bring froth to thee. Gen.3.