Definition, synonyms and related words
Initialism of Change Segment Status. (A GDS code used on older types of airline keyboards)
"The legacy flight reservation system required an agent to input CSS as a change segment status when updating the ticketing record on the vintage keyboard."
In plain English: CSS is code that tells web browsers how to style and arrange websites so they look good on your screen.
"The developer spent hours tweaking his css to make the website look more professional."