The current buzz-word in high-end food circles these days is “Umami”. It’s a Japanese-coined word based on “Umai”, meaning “tasty” (although as a kid I’d say “Umeh”, which is the slang version of “Umai”…most men would also say “Umeh” as well…as a girl or lady, I’d actually say “Oh-iishii”, which means delicious/tastes good).
On Wikipedia it is described as the 5th category of taste: a sort of savoury taste that is very satisfying to the taste-buds, the special something that gives food a particular depth of flavour:
http://en.wikipedia.org/wiki/Umami
I like to think of it in a similar way to a great perfume. You have top/head notes, middle/heart notes and bottom/base notes in a great perfume: