·noun A Serpent.
II. Adder ·noun ·same·as Sea Adder.
III. Adder ·noun One who, or that which, adds; ·esp., a machine for adding numbers.
IV. Adder ·noun In America, the term is commonly applied to several harmless snakes, as the milk adder, puffing adder, ·etc.
V. Adder ·noun A small venomous serpent of the genus Vipera. The common European adder is the Vipera (/ Pelias) berus. The puff adders of Africa are species of Clotho.