To give so much of something that it cannot be taken care of; to weigh down by so much of something that you cannot do anything about it. Usually used in the passive.
Загрузить чем-нибудь, обычно работой, настолько, что это становится невыполнимым. Обычно используется в пассивном залоге.
The busy season snowed us all under with too much work.
В разгар рабочего сезона мы все были завалены работой.
The disabled girl was snowed under with Christmas letters.
The factory received so many orders that it was snowed under with work.