In the UK mooching means going for a
walk (usually looking for somewhere to eat) often while drunk and/or
stoned.
In the US mooching is
one person taking advantage of another.
(Two guys drunk in a tent in
England)
John: "Where's Dave gone?"
Jack: "He went mooching off in that direction a couple of minutes ago"
(Two guys talking about friend's girlfriend in America)
John: "Dave's just bought his girlfriend a new car"
Jack: "She's just mooching off him coz he's rich"