the kind of intellectual who converts messages from a code to plain text
"The decoder carefully analyzed the encrypted transmission to convert it into readable intelligence for the field agents."
a machine that converts a coded text into ordinary language
"The ancient decoder successfully converted the mysterious cipher on the stone tablet into readable Latin verses."
A person who decodes secret messages
"The skilled decoder spent hours translating the intercepted cipher into readable intelligence."
In plain English: A decoder is something that turns coded information back into normal language so people can read it easily.
"The decoder on my TV remote allows me to watch all the premium channels included in our subscription package."
The word decoder comes from combining the verb decode with the agent suffix -er to describe someone or something that performs decoding. It entered English as a straightforward formation based on the existing term decode rather than having an older root meaning.