cudweed, in botany, a genus of the syngenesia... syngepsia polygamia superflua clas. The receptacle is naked; the pappus is plumose; and the calyx is imbricated. There are 41 species, five of them natives of Britain, viz., the dioicum, mountain cudweed, or cat's foot; the margaritaceum, or American cudweed; the luteo-album, or Jersey cudweed; the sylvaticum, or upright cudweed; and the uliginosum, or black-headed cudweed.