"Decrypted" is the term given to the upgraded uncroaked (or "popped again") Wanda creates after attuning to the Arkenpliers. Decrypt is used as a verb (he was decrypted), an adjective (a decrypted unit), and a noun (decrypted retain their stats), similar to the usage of uncroaked. Decrypted superficially appear to be alive, lacking the physical evidence of the trauma that croaked them.
Unlike uncroaked units, decrypted units do not decay.Erf-b1-p145
Decrypted are loyal to the tool wielder, regardless of past allegiances, but still remember their past loyalties, any information they knew in the past, and loves. Erf-b1.5-p033
Decrypted units have zero upkeep cost and their full pre-death strength.Erf-b1-p145
The unit is enslaved to either Wanda, Parson, Stanley, or the Gobwin Knob side, and may suffer a major mental attitude adjustment (e.g. "You were correct, of course. Royalty is obsolete."Erf-b1-p145) possibly due to a change in its Natural Thinkamancy or a choice made by Wanda at the time of decryption; otherwise, the Unit retains all of its previous stats, abilities, and levels, but it may suffer a demotion if it was of a high rank and that position is already occupied by another Unit.
As with uncroaking, uniforms and insignia are changed when the uncroaked join their new side. Decrypted seem to gain Wanda's insignia Erf-b1-p144 rather than the insignia of their chief warlord Erf-b1-p116, but this is Wanda's choice for units she creates Erf-b1.5-p026 rather than a feature of decryption itself. Units like Wiener-Rammers with no uniform may suffer a change of color in skin or fur.Erf-b1-p146
Wanda may be able to see through her units eyes, and if not, they will tell her anything relevant that happened to them. Erf-b1.5-p044
Although decrypted units do not decay, it is not clear whether or not they are still capable of gaining experience.
Assuming that Wanda managed to decrypt at least one Gobwin, the fact that Stanley hasn't been able to obtain any new Gobwin allies suggests that decrypted natural allies can't produce new members of their former unit type.
Real World References
Decryption, in the real world, is used as the opposite of encryption, that is protecting data by turning it into a seemingly random sequence of symbols by means of a cypher and a key. Decryption is the opposite process, which takes useless gibberish and turns it into useful information, paralleling the process of taking a useless corpse and turning it into a useful creature. The same term is sometimes also used for removing desired content from protected sources (such as DVDs, music files and books). In this case, Wanda might have gained the ability to effectively remove the "DRM" from enemy units, allowing her to raise them without penalties and under her control.
This makes the term a double pun, the 1st one being on "getting the unit out of a crypt".