Spontaneous second language acquisition (and the genesis of pidgins) involves the gradual relexification of the native or source language with target-language vocabulary. After relexification is completed, native language structures alternate with structures acquired from the target language.
Conlangs and jargon
In the context of constructed languages, jargons, and argots, the term is applied to the process of creating a language by substituting new vocabulary into the grammar of an existing language, often one's native language.
While the practice is most often associated with novice constructed language designers, it may also be done as an initial stage towards creating a more sophisticated language. A language thus created is known as a relex. For instance, Lojban began as a relex of Loglan, but the languages' grammars have diverged since then. The same process is at work in the genesis of jargons and argots such as these:
Muysken, Pieter (1981), "Halfway between Quechua and Spanish: The case for relexification", in Highfield, Arnold; Valdman, Albert (eds.), Historicity and variation in creole studies, Ann Arbor: Karoma, pp. 52–78
Singler, John Victor (1996), "Theories of creole genesis, sociohistorical considerations, and the evaluation of evidence: The case of Haitian Creole and the Relexification Hypothesis", Journal of Pidgin and Creole Languages, 11 (2): 185–230, doi:10.1075/jpcl.11.2.02sin
Wardhaugh, Ronald (2002), "Pidgins and Creoles", An Introduction to Sociolinguistics (fourth ed.), Blackwell Publishing, pp. 57–86
Wittmann, Henri (1989), "Relexification et argogenèse," Communication, 1er Colloque international d’argotologie, Université de Besançon, Oct. 13-1, 1989
Wittmann, Henri (1994), "Relexification et créologenèse"(PDF), Proceedings of the International Congress of Linguists, Québec: Presses de l'Université Laval, 15 (4): 335–38