What does "active service" mean?

Full-time occupation in the military.

What is a synonym for "active service"?

Common synonyms include: duty, selective service, service.

noun

noun ·Rare ·Advanced level

Noun

1
Full-time occupation in the military. UK, uncountable
"She was built by William Denny & Bros. Ltd., and launched in 1939, but went immediately on active service as a trooper [troopship]."

"She was built by William Denny & Bros. Ltd., and launched in 1939, but went immediately on active service as a trooper [troopship]."