Refers to languages originating in the West, especially European languages. Often used in contrast to Japanese or other Asian languages.
He can speak several Western languages.
This word is a loanword from a Western language.
欧米語 is similar but explicitly includes both European and American languages; 西洋語 is more traditional and may focus on European languages.
Compound of 西洋 (せいよう, 'the West') and 語 (ご, 'language').