[paul.fr]

Is it clearly defined, like terrestrial maps of towns/city/distracts or borders?

[DoctorBeaver]

That's a good point; and it depends how you define "solar system". It could be said that the outermost planetary orbit defines the boundary, but that doesn't allow for comets.

Personally, I think the Oort cloud should be taken as the boundary, The objects there are still bound by our sun's gravity. Once past there, though, our sun has very little effect and you truly are into the realm of interstellar space.

[daveshorts]

I think there is a definition involving how far out the solar wind  gets. So basically how far out all the high energy protons etc are travelling away from the sun and not in what ever direction the local galactic wind is blowing in. I think that one of the voyager probes has gone through this 'edge' recently.

[DoctorBeaver]

Dave - I remember reading something about that. Wasn't it an unexpected shape, or something like that? I didn't realise that was classed as the edge of the solar system though.

[Raliel]

The Heliosheath is the actual boundary of the Solarsystem, a sort of wierd tidal ring of slow moving solar winds combined with gasses from outside the system

[dentstudent]

Is it not the heliopause, the edge of the heliosheath? Or even the bow-shock as it's still related to the presence of the solar-wind?

[Soul Surfer]

There is one other border beyond those mentioned that is in theory clearly defined (but changes continuously) That is the gravitational border between the sun and our nearest neighbour stars.  This is probably best defined as the point where an object that is stationary with respect to the sun would fall towards the sun by it's gravitational field as opposed to fall towards the other nearby star.

[edward2007]

Have a look here:

http://www.answers.com/topic/heliopause

Scroll down to the picture.

Edward