According to the American Meteorological Society, there are very specific criteria for blizzard conditions. They are winds of at least 35 mph and visibilities reduced by falling and/or blowing snow to less than ¼ mile for at least three consecutive hours.
Notice there is not a snowfall amount in the definition. Just a few inches of snow could create blizzard conditions with blowing snow (often called a “ground blizzard”). Also, a heavy snow with no wind would also not be considered a blizzard.