A reservist is someone who belongs to the reserve: the extra part of an army, navy, or air force that a country keeps ready, but who is not a full-time soldier in ordinary life.

A reservistreservist（後備軍人） is someone who belongs to the reserve指屬於reserve（後備部隊）的人 the extra part of an army, navy, or air force也就是陸海空軍額外保留 that a country keeps ready讓國家隨時可以動用的那部分兵力 but who is not a full-time soldier in ordinary life但平常並不是全職軍人

Most of the time they have another job — teacher, driver, student — and they train now and then. If a war or a serious emergency comes, the government can call them up.

Most of the time they have another job大部分時間他們有另一份工作 teacher, driver, student像是老師、司機、學生 and they train now and then偶爾會接受訓練 If a war or a serious emergency comes如果戰爭或重大緊急狀況發生 the government can call them up政府就可以徵召他們

News and official talk use the word a lot; it is not a chatty kitchen-table word.

News and official talk use the word a lot新聞和官方用語常常用這個字 it is not a chatty kitchen-table word不是餐桌閒聊會用的詞

People sometimes stretch it to anyone kept “on the bench” in a company, though actually it still smells of the military, and that looser use can sound like showing off.

People sometimes stretch it有些人會把這個字延伸使用 to anyone kept 'on the bench' in a company指公司裡被留著'on the bench'（備用）的人 though actually it still smells of the military不過其實還是帶著軍事的味道 and that looser use can sound like showing off這種鬆散的用法聽起來會像在故作誇張

The reserve is the group; a reservist is one person in it.

The reserve is the groupreserve指的是整個群體 a reservist is one person in itreservist則是其中的一個人