Definition of swallow-wort:
(n) :
Plants of genus Vincetoxicum, especially Vincetoxicum nigrum (syn. Cynanchum nigrum, black swallow-wort) or (Vincetoxicum hirundinaria (syn. Cynanchum vincetoxicum, white swallowwort).
(n) :
Plants of genus Cynanchum
(n) :
A plant of any of several species of plants whose parts resemble a swallow's tail:
(n) :
In genus Asclepias (milkweed):
(n) :
orange swallow-wort (Asclepias tuberosa)
(n) :
silky swallow-wort (Asclepias syriaca