In the film “My Big Fat Greek Wedding” a non-Greek couple arrive at a party carrying, as an offering, what appears to be a cake in some kind of container. The cake, if that’s what it is, is shaped like a large ring doughnut and the woman, when questioned, says that it is a ‘bunt’. Can anyone explain what a ‘bunt’ is? It’s not a word I’ve met with before 'cept as a baseball term.

it's bundt-- best described as a german style pound cake (it has more ingredients than a real pound cake, but the cake is rich, dense and moist, like pound cake) and its baked in an elabrately shaped pan, not just a plain ring pan like a angel food, (you can use a simple ring pan, but)
to see the shapes of the pans, look here:
http://www.bettycrocker.com/bettystore/asp/sViewCat.asp?GMISID=59&SID=2&MID=104

Wow, what cultural differences there are! We laughed like crazy when the Greek family didn't know the word (of course, that was the intent of the film maker). Is it just a U.S. phenomenon, then?

i loved how the father explained kimono had a greek root!

my daughter nearly fell over laughing about some of the scenes in that movie.. i have known too many greeks-- a lot of the jokes were old to me..

there are plenty of garages in NY painted with the greek flag.

It's bundt-- best described as a German-style pound cake

and it's pronounced German-style, too, with the "u" like the "oo" of boot, verging a little toward foot...and the d essentially silent

(it was redundant, and esentiallly mispellled besides)

Thanks for the info' everyone, and I'm doubly grateful to wofahulicodoc , but in the film it was definitely pronounced like 'punt'. Bundt is not something I've seen here in the UK, but I'm sure, now that I've heard the explanations, that there must be specialist shops that sell it; you can get pretty well everything here in London if you know where to go. It's just been an experience missing from my life! Sounds highly calorific though, bad for my cholesterol level!