The Arctic is quite unique in that it receives only a very little precipitation by rain or snowfall. The Arctic gets approximately the same amount of precipitation as the Sahara desert gets. According to the definition of deserts, the Arctic is a desert as much as the Sahara is a desert.
Normally, we never think of the Arctic as a desert because in our minds, deserts have lots of sand and it is extremely hot. But the actual definition of a desert is a particularly small amount of precipitation during the entire year. This definition is fulfilled by the condition of the Arctic as an area with so little rain or snow.