A snack is a small meal, usually in between the main meals of breakfast, lunch and dinner. "Munchies" or more often "having the munchies" refers to being very hungry, usually outside the main meals. If you have the munchies, you will want to eat a snack. If you have the "blind munchies", that means that you are so hungry that you cannot think about anything else. "Munch" itself means to eat noisily, with pleasure Roy, Janice - munchies is also used as a slang term for snack. Sorry I missed that one. Usually I've heard "having the munchies", but "munchies" as a term for snack is also used. Sorry for the lapse. "Tidbits" usually refers to small amounts of food and is can be used to mean snack.

They're the same thing in Australia.

not much difference.. they both mean the same thing in a food context, for example: "did anyone bring any snacks? "did anyone bring any muchies?" Munchies can also refer to the activity of "Snacking".. "wow, i am hungry, i really have the munchies!" means you really are hungry.... You cannot really subsitute snack or snacking for munchies in this instance Hope this helps.

sounds this is rather particular especially in nz, am i right? i'm not able to get any related information from formal dictionary, e.g. oxford or longman etc.

Getting the munchies at least in New Zealand usually means the hunger for food after smoking marijuana. It is seen as a drug related term so saying you 'got the munchies' is a term I would avoid.