1. One who exhibits machismo
2. Machismo

(abbreviation for massive astrophysical compact halo object) Component of the Galaxy's dark matter first identified 1993. Most MACHOs are believed to be brown dwarfs, tiny failed stars with a mass of about 8% that of the Sun, but they may also include neutron stars left behind after supernova explosions. MACHOs are identifiable when they move in front of stars causing microlensing (magnification) of the star's light. Astronomers estimate that they account for 20% of the dark matter.

Excessively masculine; aggressive; swaggering.