2. (Science: zoology) a small venomous serpent of the genus Vipera. The common European adder is the Vipera (or Pelias) berus. The puff adders of Africa are species of Clotho. In America, the term is commonly applied to several harmless snakes, as the milk adder, puffing adder, etc.
same as sea adder.
Origin: oe. Addere, naddere, eddre, as. Naedre, adder, snake; akin to os. Nadra, OHG. Natra, natara, Ger. Natter, goth. Nadrs, Icel. Naor, masc, naora, fem., cf. W. Neidr, Gorn. Naddyr, ir. Nathair, L. Natrix, water snake. An adder is for a nadder.