The Collaborative International Dictionary of English v.0.48:

Cid \Cid\, n. [Sp., fr. Ar. seid lord.]
   [1913 Webster]
   1. Chief or commander; in Spanish literature, a title of Ruy
      Diaz, Count of Bivar, a champion of Christianity and of
      the old Spanish royalty, in the 11th century.
      [1913 Webster]

   2. An epic poem, which celebrates the exploits of the Spanish
      national hero, Ruy Diaz.
      [1913 Webster]

WordNet (r) 3.0 (2006):

CID
    n 1: the United States Army's principal law enforcement agency
         responsible for the conduct of criminal investigations for
         all levels of the Army anywhere in the world [syn:
         Criminal Investigation Command, CID]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

CID
       Configuration - Installation - Distribution (IBM)


The Free On-line Dictionary of Computing (30 December 2018):

Caller ID
CID

    (CID) A short piece of text transmitted by
   some telephone systems describing the origin of a call,
   e.g. the name of the caller.  Some telephone handsets can
   display this.  A computer telephony integration system might
   use it to trigger actions on the callee's computer such as
   looking up the caller in a database and displaying their
   details on screen.

   There may also be a separate "caller id number" giving the
   telephone number of the originator of the call.

   (2008-04-30)