plain text definition by American Heritage Dictionary
plain text - Computer Definition
Data comprising standard characters (e.g., letters, numbers, and punctuation marks), with no formatting codes. Such unformatted text usually is coded according to the ASCII standard, which adequately represents the characters and symbols used to form the words used in most spoken languages and which, therefore, lends itself to text-to-speech (TTS) conversion. See also ASCII, data, rich text, and TTS.