1. To surround something with snow, rendering it impassable, immovable, or inoperable. Often used in passive constructions. In this usage, a noun or pronoun can be used between "snow" and "in." Traffic on the interstate was so bad that the snowstorm that blew through actually ended up snowing many of cars in, causing even more traffic problems as a result. I just got a call from the ski lodge. Apparently they were snowed in by the blizzard last night, and there's no way to get in or out of the place at the moment.

2. To cause someone or something to be unable to leave a building or area due to the snow. Often used in passive constructions. In this usage, a noun or pronoun can be used between "snow" and "in." We were snowed in for several days, with only a small cupboard's worth of food to subsist on.