A 3d engine is just that, a realtime renderer that can be used for games.. or something else. Theoretically, it provides a host of additional facilities for rendering a scene above and beyond what is provided in a lower level 3d framework like Direct 3d.
A game-engine is altogether different. It includes a rendering system, as well as systems for AI, collision detection, and everything else required by your core game application.
Further, I would say that a 'game engine' is a singular integrated system of frameworks and facilities that were designed and intended to work specifically together in the support of a game application. By that I mean that if you take a 3d engine, a physics engine, a AI framework, and sundry bits and pieces of cool tech from here and there, you will never reach a point where you have a 'game engine'. You can certainly use all of those things to make a game, but it will require a substantial amount of glue code that is simply not necessary with a 'game engine'.
That is why Ogre is not a game engine, no matter how many extra parts you can download with it, and Panda is. When you see alot of these projects with these feature sets, make sure you know what you are getting. It does not matter if it includes a physics engine or anything else, if its not a game engine you will have to write one to get from those pieces and parts to an actual game...