Critical Infrastructure Sectors definition in Computer Security terms:
Definition(s): Information technology; telecommunications; chemical; transportation systems, including mass transit, aviation, maritime, ground/surface, and rail and pipeline systems; emergency services; and postal and shipping.
Source(s): CNSSI 4009-2015 (NIST SP 800-30 Rev. 1)
NIST SP 800-30 (HSPD-7)
reference: CSRC Glossary