The point corresponding to the centre of mass of the planets in the solar system, which the planets orbit. The Bary Centre is normally close to the centre of the Sun.
This is used to classify stars. The German astronomer Johann Bayer 1572 - 1625 assigned letters from the Greek alphabet to the brightest stars in each constellation. They usually followed the order of Alpha for the brightest, Beta for the 2nd brightest, and Gamma for the 3rd brightest etc.
The benefic planets are Venus and Jupiter. The Waxing Moon (increasing in light) is also considered to be benefic. The effects of benefic planets are generally favourable.
A planet is besieged if falls between, and is in orb of, two other planets. A planet rejoices if it is besieged by benefics and is afflicted if besieged by malefics. Traditionally, a besieged planet lay between Mars and Saturn and in the same sign, however, common usage allows for a planet to be besieged if the outer two planets are in different signs.
The Black Moon is a mathematical point that corresponds to position of the Moon when it is at Apogee (that point in its orbit when it is farthest from the Earth). The point opposite the Black Moon is called Priapus.
The Black Sun is a mathematical point that corresponds to the position of the Sun when it is at Aphelion (that point in its apparent orbit when it is farthest from the Earth).