red ink is a noun meaning "the amount by which the cost of a business exceeds its revenue". It carries one recorded sense.
the amount by which the cost of a business exceeds its revenue
“the company operated at a loss last year”
“the company operated in the red last year”
Definitions, synonyms and semantic relations for red ink come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.