The Collaborative International Dictionary of English v.0.48:

Macho \Ma"cho\, n. [Sp.] (Zool.)
   The striped mullet of California (Mugil cephalus, syn.
   Mugil Mexicanus).
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

macho \ma"cho\, a. [Sp.]
   Manly, especially with an assertive and domineering manner
   toward women.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

MACHO \MACHO\ (m[aum]"k[-o]), n. [acronym from Massive
   Astrophysical Compact Halo Object.]
   A form of dark matter in distant outer space unobservable
   except by its gravitational effect, and believed to be at
   least part of the "missing matter" which is unobservable as
   ordinary stars, but helps keep galaxies from flying apart;
   MACHOS are massive but compact objects such as neutron stars
   or brown dwarfs, which can be detected (with difficulty) by
   their effect in bending light from distant light sources,
   such as other galaxies. This can occur if by rare chance a
   MACHO passes in front of a more distant visible object, and
   the light from that object becomes temporarily amplified by
   the MACHO acting as a gravitational lens. Some MACHOs have
   been discovered in the halo of dark matter that surrounds our
   milky way. It is, however, questionable whether the amount of
   such matter is sufficient to explain the ability of galaxies
   to stay together in spite of rotation rates that would cause
   them to fly apart if the only matter present was that
   observable as visible stars.
   [PJC]

WordNet (r) 3.0 (2006):

macho
    adj 1: used of men; markedly masculine in appearance or manner
           [syn: butch, macho]
    n 1: a male exhibiting or characterized by machismo