Used attributively, chiefly in compound nouns, to describe something connected with submarines or acting as a substitute.
Definitions
Relating to or characteristic of a submarine. The sub crew prepared the vessel for a long deployment.
Serving as or involving a substitute. He played a sub part while the lead actor recovered.
Used attributively, e.g. "sub patrol", "sub fleet".
Definitions
Relating to or designed for submarines or submarine operations. The navy increased its sub capabilities in the Arctic.