1 [mass noun] the action or process of registering or of being registered:the registration of births, marriages, and deaths [count noun]:the number of new private car registrations has increased
[count noun] a certificate that attests to the registering of a person, car, etc..
the action or process of acquiring full British citizenship by a Commonwealth resident or a person of British descent:in certain cases, children may acquire British citizenship through registration
2 (also registration mark or registration number)British the series of letters and figures identifying a motor vehicle, assigned on registration and displayed on a number plate:her car registration is H53 UVO
3 [mass noun] Music a combination of stops used when playing the organ.
mid 16th century: from medieval Latin registratio(n-), based on Latin regerere 'enter, record' (see register)
registration in other Oxford dictionaries
Definition of registration in the US English dictionary