horizontal script; European writing; Roman letters
Refers to writing that runs horizontally, especially European languages using the Roman alphabet. Often contrasted with vertically written Japanese script.
彼は横文字の看板を指さした。
He pointed at the sign written in horizontal script.
This document is written in horizontal script.
European language; Western language
By extension, refers to a European or Western language itself, often with a nuance of foreignness or difficulty.
横文字ばかりのメニューで何を頼めばいいかわからなかった。
The menu was all in a Western language, so I didn't know what to order.
He's not good with Western languages, so it takes him a long time to read English materials.
The sign was written in Roman letters.
I think recent business emails use too many Western loanwords.