A macho sub is a sub, or submissive person, who likes to push the limits of what they can endure. The pride macho subs feel in their ability to withstand pain or punishment is a key part of their identity.
Rather than showing distress or ending a scene, macho subs would rather endure whatever treatment their dominants deliver, even if it is not pleasurable. They are unlikely to offer spontaneous feedback about their discomfort. Macho subs are often driven by a desire to please their dominants, to prove themselves to be good submissives, and to never appear weak or wimpy.
The term macho sub is short for macho submissive. A macho sub may also be called a macho slave.