The boat moved out into midstream. The politician tried to change platforms midstream.

Stream is the root word of midstream.

The root word of midstream is "mid" which means in the middle or center.

Magellan Midstream Partners is a company acquired by Riverstone Holdings, a private equity firm, in 2003. The company was originally named Magellan Midstream until it acquired subsidiaries, and was rebranded as Magellan Midstream Partners.

I believe a CC midstream urinaylsis is referring to a "clean catch midstream UA" In other words, you wipe with a cleaning towelette according to the directions, then you begin to urinate and before you are finished, you will catch some of the urine whil in midstream.