A biceps slicer (also called a biceps lock or biceps crusher) is a compression lock that involves pressing the biceps into the humerus. An effective biceps slicer can be applied by putting an arm or leg as a fulcrum on the opponent’s arm at the inside of the arm by the elbow, and flexing the opponent’s arm over the fulcrum. This will result in the biceps and forearm being pressed into the fulcrum.
The biceps slicer becomes most effective as a compression lock when the bony parts of the limb such as the shin or any of the bones in the forearm are forced into the biceps of the opponent. The biceps slicer can also become a potent armlock when it is applied in this manner, because the leverage causes an elongating and separating tension in the elbow joint, making this a legal technique in judo competition.
In Brazilian jiu-jitsu competitions however, the biceps slicer is an illegal technique in lower level divisions of some major tournaments. In catch wrestling biceps slicer variation is called short-arm scissors.
This bicep slicer happened at the Summit Fighting championship in 2015, and it was an amateur MMA fight, you can hear the bicep pop:
How to do a Bicep Slicer from Spider Guard With Carlson Gracie Black Belt Alain Guerra Pozo: