Of Scottish/Glaswegian derivation: rotten, gone bad
'Oi David, sniff the milk and see if its foosty'
by whiskymack February 21, 2004
Musty, mouldy, smells bad.
The bread's foosty already! Oh, it's a week past it's sell-by date.
by Keemy October 02, 2005
When something smells kinda bad.....
Boy, that poop I did was foosty last night
by The Naeblis October 22, 2004