back end

Short definition from Wiktionary

Noun

1. 1
   The rear, back, or unseen portion (of something).
2. 2
   That part of a hardware or software system that is farthest from the user; the internals rather than the user interface.
3. 3
   The latter end of any given time, especially the latter part of the year; autumn; late autumn.
4. 4
   Money paid on a contingent deferred basis, for example, as a proportion of the profits or revenue of a work.
5. 5
   The processing of spent fuel from a nuclear reactor into reusable materials.
6. 6
   Alternative form of back end.

Adjective

1. 1
   Relating to the back end part of a hardware or software system.