noun
full-back (soccer)
Wasei-eigo term used in Japanese soccer for a full-back position.
wasei-eigo (Japanese-coined English), from sideback
彼は高校サッカー部でサイドバックを務めている。
He plays full-back for his high school soccer club.
フルバック is a more direct loanword for 'fullback' in rugby or American football, while サイドバック is a wasei-eigo term specific to soccer.
Wasei-eigo from English 'side' and 'back', referring to the full-back position in soccer.