To have reduced something substantially, to the point where said thing is no longer sufficiently complete to be considered to be that thing, prior to an action's being performed to reconstitute it.
Note: Reconstitution may require a single simple step (such as adding boiling water), or a complex plurality of steps, but the potential for returning said thing to its original form must have been intended for deconstitution to have taken place. If reconstitution was not intended, then the thing was merely destroyed/consumed/ruined etc.
Son: "Do we have any Thai green curry left?"
Mom: "Sure, it's in the cupboard. It's deconstituted, though, so you'll need to add two cans of coconut milk, some basil, and toss in some chicken meat, and then cook it on medium-high for about 10 minutes."
Son: "So that's a "no", then."
Lawyer: "I got those files you sent me in my email, but I can't do anything with them. I sent them to my IT people, and they couldn't even identify what they were supposed to be? They must have become corrupted in transfer."
Client: "No, no - they were deconstituted, on purpose, for security reasons. I don't trust public key crypto, and these documents contain critical stuff which is for your eyes & ears only. Now that I have you on the phone, I'll give you the link and password for where you can get the reconstitution tools and the holdback portion, so you can decode them."
Lawyer: "Cool! Give'em to me... Wait, did you say "eyes and ears"?
Client: "Yeah, there's two textual documents, four image files, and a 5 minute video of me explaining how the process works, for your patent guys. Anyway, point your browser to ....., and login as your last name, with the password 'bananahammock'"