The IRIS-4D series of servers and workstations from Silicon Graphics

Class 4-D, a classification of the Selective Service System

Cinema 4D - a commercial cross platform 3D graphics application

Air Sinai - IATA code

The Fourth dimension (disambiguation)

4D - Time-lapsed series of 3D earth models

4-D, a psychedelic drug.

4-D film - combines 3-D film and physical effects

4D (train) in Melbourne, Australia

4-Digits - a lottery in Malaysia and Singapore