Supersetting antagonising is the pairing of two opposite muscle groups such as chest and back, triceps and biceps and quads and hamstrings. (womenshealthandfitness.com.au)
Training opposite muscle groups optimizes the number of contracting muscles fibers, which in turn increases the weights being lifted and helps with anabolic hormone production. (fitnessandpower.com)
You will mix exercises that hit opposite muscle groups: (fitnessandpower.com)