Here is the definition of DE by Eugene Nida himself. Note the importance of reader response in his concept, and also note some of his methods based on transformational grammar. In Nida's definition, DE does not occur without allowing for reader response by means of transformations. (Words in all caps are defined elsewhere in his glossary.)
"dynamic equivalence: quality of a translation in which the message of the original text has been so transported into the receptor language that the RESPONSE of the RECEPTOR is essentially like that of the original receptors. Frequently, the form of the original text is changed; but as long as the change follows the rules of back transformation in the source language, of contextual consistency in the transfer, and of transformation in the receptor language, the message is preserved and the translation is faithful. The opposite principle is FORMAL CORRESPONDENCE."
The Theory and Practice of Translation, by Eugene Nida and Charles Taber, 1982, p. 200.