1. Small terrestrial viper common in northern Eurasia
   "The adder basked in the morning sun on a rocky outcrop";
   - common viper, Vipera berus
    
2. A person who adds numbers
   "Before calculators were common, skilled adders were valued in accounting firms"
    
3. A machine that adds numbers
   "Before electronic calculators, mechanical adders were used for bookkeeping"

Derived forms: adders

Type of: calculating machine, calculator, computer, estimator, figurer, reckoner, viper

Part of: genus Vipera, Vipera

Encyclopedia: Adder