Anonomously rejecting a trade between opposing players in fantasy football all the while crying yourself to sleep every night because your team is the worst thing to ever happen to the sport. This is basically a cock block in the world of fantasy sports and the two can be used interchangably.
"Someone pulled a Marshall and my trade didn't go through."
"Son of a bitch! Someone's team must suck because my trades keep getting rejecting, who's the Marshall this time."
"Did you see Kyle pull that Marshall on Bshaw? He totally got cock blocked yo!"