Adder

Add·er

Adder

n.
  1. One who, or that which, adds; esp., a machine for adding numbers.

Adder

n.
  1. A serpent. [Obs.]
  2. A small venomous serpent of the genus Vipera. The common European adder is the Vipera berus [or] Pelias berus. The puff adders of Africa are species of Clotho. (Zool.)