A species of serpent, more commonly called viper. The word adder is used five times in the Bible, as a translation of four different serpents of the venomous sort. In Genesis 49:17 , it seems to mean the cerastes, or horned viper, of the color of sand, and very deadly bite; accustomed to lie hidden in the tracks in the sand, and dart up on the unwary traveller. In Psalm 58:4 91:13 , it is probably the asp. In Psalm 140:3 perhaps the tarantula, or some serpent that strikes backwards. See SERPANT, VIPER.