CID

plural CIDs

1. countableuncountablecaller identification; a feature that identifies the phone number of the caller.
2. abbreviationcountableuncountableAbbreviation of combat identification; compare IFF.
3. abbreviationacronymcountableuncountableAcronym of center/centre instrument display.
4. abbreviationcountableinitialismuncountableInitialism of criminal investigation/investigative division/department.
5. abbreviationcountableinitialismuncountableautomotiveInitialism of cubic inches displacement; cubic inches of displacement.

1. UKinitialismgovernmentScotland Yard's Criminal Investigation Department

   And I am quite sure that Max Carrados won't walk in here without making it certain that if he doesn't soon come out again the C.I.D. will smash down the door if need be to find out what has happened.

   1934, Ernest Bramah [pseudonym; Ernest Brammah Smith], The Bravo of London

2. USinitialismgovernmentU.S. Army Criminal Investigation Command
3. USinitialismgovernmentFormer name of NCIS (Naval Criminal Investigation Division).