System D (in French, Système D) is a shorthand term that refers to a manner of responding to challenges that requires one to have the ability to think fast, to adapt, and to improvise when getting a job done. The letter D refers back to either of the French nouns "débrouille", débrouillardise or démerde (French slang). The verbs se débrouiller and se démerder mean to make do, to manage, especially in an adverse situation.