a day on which public schools or other institutions are closed due to heavy snow.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
Examples from the Web for snow day
Naturally the effect on his complexion of the first snow-day quite horrified our Adonis.Italian Alps|Douglas William Freshfield
British Dictionary definitions for snow day
US a day on which heavy snow makes it impossible for children to attend school
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012