noun
Obsolete military term for the lowest rank in the Japan Self-Defense Forces, roughly equivalent to a recruit or private. No longer in active use.
かつて自衛隊では、入隊直後の隊員は三士と呼ばれていた。
In the past, newly enlisted members of the JSDF were called 三士.
From 三 (three) and 士 (soldier/warrior), likely indicating the third or lowest tier of soldier ranks in the JSDF system. The exact historical derivation is uncertain.