Western writing; Western text
Refers to text written in a Western language, or a sentence/word from a Western language. Often used in contrast to Japanese or Chinese writing.
He received a letter written in a Western language.
calque; loan translation
A word or expression formed by translating the components of a Western word into Japanese, such as 鉄道 for 'railway'. This sense is more technical and less common than sense 1.
The word 洋文 itself can sometimes refer to a word created by translating a Western term.