[davidw]

"E se me nona gavesse e rode sarìa na carioea", as they say here in the Veneto, which, literally translated, means "if my grandmother had wheels, she'd be be a wheelbarrow".

[eric_the_read]

Along the same line, "If a pig had wings, it'd be a pigeon." I want to say that's from Heinlein, but I'm not positive.

[krisoft]

In Hungary I heard the same saying, just with streetcar instead of wheelbarrow. Funny how these things tend to spread.

[geon]

And what does it mean?

[davidw]

The literal translation is pretty clear, actually. If [something ridiculous/impossible] then [something else ridiculous/impossible]. In other words the comparison is a bit of a stretch.