What does the 'constitutionalisation' of the EU actually mean?

I'm writing an essay at the moment on the constitutionalisation of the EU and have lots of research on the 'constitutionalising principles' such as direct effect and supremacy. What I'm still not entirely clear on, though, is the meaning of 'constitutionalisation'. It seems like such a loose concept which could actually be given varying meanings, so I'm looking to see how TSR's resident lawyers and law students would define it.

I don't know what 'constitutionalisation' is, but if it has anything to do with constitutionalism there are likely to be as many definitions of it as there are commentators on the topic. In the face of the the risk of your essay getting mired in semantics, it is probably better to first assess the substance of the EU's institutional structure and then discuss the applicability of the 'constitutionalisation' term later. What is it to 'constitutionalise' something? There's room for some interesting discussion there, but I think that should follow an appraisal of the state of the EU 'on the ground', rather than preceding it.