reverse engineering

Short definition from Wiktionary

Noun

1. 1
   The process of analyzing the construction and operation of a product in order to manufacture a similar one.
2. 2
   The process of analyzing the construction and operation of a product in order to manufacture a similar one: Such analysis of an executable or other system in order to recreate its workings.

Verb

1. 1
   present participle and gerund of reverse engineer
2. 2
   present participle and gerund of reverse-engineer