Per the usual definition, a "bad" Major League Baseball trade involves one team making out like gangbusters while the other one ends up with a whole lot of nothing.

But what if we were to redefine a "bad" trade as one in which neither party got what it wanted?

Allow us to illustrate by recounting the 10 biggest blockbuster trade busts of the 21st century. These are deals in which a buyer was banking on at least one established star, with the seller placing its hopes in prospects and other building-block types. But in the end, it was all for naught for everyone.

Let's start with some honorable mentions and then count down the top 10 based on just how badly they backfired. 

Honorable Mentions

Aug. 11, 2008: The Adam Dunn Trade

The Deal: Arizona Diamondbacks get OF Adam Dunn (-0.4 rWAR); Cincinnati Reds get RHP Micah Owings (-0.9), INF/OF Wilkin Castillo (-0.1) and RHP Dallas Buck (0)

Dunn did hit eight home runs in 44 games for the Diamondbacks, but they still missed out on a second straight postseason. The trade was otherwise a case of the Reds trying to get something for Dunn before free agency called his number that winter, but none of the three prospects they got back panned out.

July 31, 2010: The Lance Berkman Trade

The Deal: New York Yankees get 1B/DH Lance Berkman (-0.3); Houston Astros get RHP Mark Melancon (1.0) and OF/INF Jimmy Paredes (-1.8)

Acquired to help bolster the Yankees offense for the stretch run, Berkman managed just a .707 OPS down the stretch of 2010. Melancon looks like a major prize for the Astros in retrospect, but it was after he left Houston that he came into his own as a star closer.

Jan. 30, 2012: The Michael Pineda-Jesus Montero Trade

The Deal: New York Yankees get RHP Michael Pineda (6.3) and RHP Vicente Campos (0); Seattle Mariners get C Jesus Montero (-1.0) and RHP Hector Noesi (-1.4)

This one worked out better for the Yankees but not as well as it could have. Pineda missed all of 2012 and 2013 with a bad shoulder, and he was inconsistent after he returned. In Seattle, Montero went from being seemingly a sure thing to one of the most heartbreaking prospect flops in recent memory.

July 14, 2016: The Drew Pomeranz Trade

The Deal: Boston Red Sox get LHP Drew Pomeranz (3.9); San Diego Padres get RHP Anderson Espinoza (0)

In spite of a respectable 17-win season in 2017, Pomeranz was largely up and down in two-plus seasons with the Red Sox following his All-Star breakout in 2016. Espinoza was an elite pitching prospect at the time, but injuries (including Tommy John surgery) have all but destroyed his professional career.