нарука́вник

nounmasculineinanimatecountablerare

1.
oversleeve, armlet, protective sleeve cover
Бухга́лтер надел нарука́вники, что́бы не испа́чкать руба́шку.
The accountant put on oversleeves so as not to dirty his shirt.
Usually worn by clerks or workers to keep sleeves clean.
2.
water wings, inflatable armband, swimming armband
Ребёнок пла́вал в нарука́вниках.
The child was swimming with water wings.
Usually plural: нарукавники.

Examples

Дети надели нарукавники и вошли в бассейн.
The children put on their arm floaties and got into the pool.
Не хочу́ хва́стать, но я уже пла́ваю без нарука́вников.
I don’t want to brag, but I can already swim without armbands.
Рабочий носит нарукавник, чтобы не запачкать рукав.
The worker wears an oversleeve so he won't get his sleeve dirty.