My Mesh Is A Wireframe In Solid And Won't Render

Hi all,
Semi-noob here. I don’t know what I did, but one of my meshes is now appearing as a wireframe even when Solid is selected while everything else in the scene appears solid. When I render, everything but the mesh in question renders. What did I do? How do I undo this?

Add a screenshot showing the whole interface or preferably upload your blend file to http://www.pasteall.org/blend/