1. to translate (secret or coded information) into ordinary language or understandable form; decipher: »
Hittite hieroglyphics…are being decoded (Newsweek). Figurative. The plot needs to be decoded and when it is, not much seems…to be taking place (Harper's).
2. to apply the spelling-sound relationship to (reading), especially in the learning process.
Useful english dictionary. 2012.