What is "blue weed"

viper \vi"per\ (v[imac]"p[~e]r), n. [F. vip[`e]re, L. vipera, probably contr. fr. vivipera; vivus alive + parere to bring forth, because it was believed to be the only serpent that brings forth living young. Cf. Quick, a., Parent, Viviparous, Wivern, Weever.]

1. (Zo["o]l.) Any one of numerous species of Old World venomous snakes belonging to Vipera, Clotho, Daboia, and other genera of the family Viperid[ae].

   There came a viper out of the heat, and fastened on his hand.
   --Acts xxviii. 3.

   Note: Among the best-known species are the European adder ( Pelias berus), the European asp ( Vipera aspis), the African horned viper ( Vipera cerastes), and the Indian viper ( Daboia Russellii).

2. A dangerous, treacherous, or malignant person.

   Who committed To such a viper his most sacred trust Of secrecy.
   --Milton.

3. Loosely, any venomous or presumed venomous snake.

   Horned viper. (Zo["o]l.) See Cerastes.

   Red viper (Zo["o]l.), the copperhead.

   Viper fish (Zo["o]l.), a small, slender, phosphorescent deep-sea fish ( Chauliodus Sloanii). It has long ventral and dorsal fins, a large mouth, and very long, sharp teeth.

   Viper's bugloss (Bot.), a rough-leaved biennial herb ( Echium vulgare) having showy purplish blue flowers. It is sometimes cultivated, but has become a pestilent weed in fields from New York to Virginia. Also called blue weed.

   Viper's grass (Bot.), a perennial composite herb ( Scorzonera Hispanica) with narrow, entire leaves, and solitary heads of yellow flowers. The long, white, carrot-shaped roots are used for food in Spain and some other countries. Called also viper grass.