1) Standing for the "North Atlantic Treaty Organisation". More inforation available here NATO site
2) A way of taking tea - NATO Standard tea is with milk and two sugars.
3) A strange threatening organisation which, according to many residents of the Florida Everglades, the Appalachian Mountains, Washington State and Alaska, is threatening to take over the USA and thus eventually 'prise their guns from their cold, dead, fingers'. Which apparently makes it alright to blow up FBI office buildings and dress your 23 stone fat, skank, girlfriend in a DPM thong.