Sentence:  Instead of overlaying secondary images by alluding to an existing literary or oral tradition, structural <WSD>overcodes</WSD> overlay the secondary images by using technical vocabulary from a different frame of reference. 
Meaning of the word marked with <WSD> tags:  An established code (signifier) that also acts as a new code, either representing additional (related) meanings, or dividing into various nuances of the original meaning.