A mother enhancer is male who sleeps with a lot of people and makes them pregnant (usually sleeps with virgins). Another way to say it is that The word "mother enhancer" has the essential meaning of making many women mothers and thinking it's cool. It can also mean an equivalent of mother fucker.
Example 1: That guy over there has had so much sex. He's probably a mother enhancer.
Example 2: I heard that some guy made Selene Gomez pregnant. He's a real mother enhancer.
Example 3: Shut up you mother enhancer!