from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of various massive dark objects, such as a brown dwarf star or large planet, in the outermost regions of a galaxy, that may explain the observed anomalous rotation of most galaxies.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- massive compact halo object
m(assive) a(strophysical) c(ompact) h(alo) o(bject).(American Heritage® Dictionary of the English Language, Fourth Edition)