Charlie Harper's Cause of Death -- 'MEAT Explosion'

TMZ has done more recon and has gotten the real lowdown on HOW Charlie Harper died -- and it isn't pretty.

Sources at Friday night's taping tell us ... Harper married Rose -- the neighbor/stalker he flew to Paris with last season -- but things went downhill quickly when she found him in the shower with another woman.

In the episode, we're told Rose speaks at the funeral and recounts what happened to Charlie ... saying the day after the shower incident she and Charlie were waiting for a Paris subway when Charlie "slipped" and the subway literally blew him apart in a "meat explosion."

The strong inclination was that Rose pushed him and got away with it.