Portable code can be run with little to no modification in multiple environments. Portable applications can be run from, for example, a USB drive without modifying a computer's environment.
Cross-browser refers to the ability of a website, web application, HTML construct or client-side script to function in environments that provide its required features and to bow out or degrade gracefully when features are absent or lacking.
What do you think about desynonymizing them? How could we handle that change?