one by one; one at a time; in turn
Used when people do something individually, each in their own turn, or when distributing items to each person.
The students entered the classroom one by one.
I handed out the presents to each person one at a time.
Standard spelling.
Rarely used kanji form; 宛 is not common for this meaning.
Compound of 一人 (ひとり, 'one person') + ずつ (adverbial particle meaning 'each' or 'at a time').