Glossary
O
A, B, C, D, E, F, G, H, I, J, K, L, M, N, O, P, Q, R, S, T, U, V, W, Y, Z

Obliquity—The angle made between the plane of the ecliptic (Earth's orbit) and the plane of the Earth's equator.
Occidental Planet—A planet that can be seen in the west after sunset, and which will be overtaken by the Sun. A planet so placed has a weak position (ie, it is accidently weak in dignity). Also called vespertine.
Occultation—The eclipse of a star or a planet, by the Moon or another planet.
Opposition Aspect—An aspect based on an arc (section of a circle) of 180°. Planets exactly opposite each other in the chart; this creates stress. The difference between two planets in opposition is six stars signs. Balance by way of additional aspects to either of the opposed planets is needed in the presence of an opposition. This is a major aspect.
Orb—Aspects are distinct relationships between planets (eg, a square is 90° apart). An orb is the number of degrees that the relationship can differ and still be effective (eg, 94° is still a square).
Orbit—The path travelled by a planet around the Sun, or by a Moon around a planet, and so on. The orbit is a balance between the planet's desire to go straight (velocity), and the attraction (gravity) of the Sun. Its shape is elliptic (like an oval, but with distinct mathematical properties), which means that the planet is sometimes closer and sometimes further from the Sun.
Oriental Planet—A planet that has just been overtaken by the Sun and can therefore be seen in the east before sunrise. A planet so placed is in a strong position (ie, it is accidently strong in dignity).
Orientations—Along with the elements (triplicity), polarities and modalities (quadruplicity), the orientations are a way of grouping the signs and houses. The three orientations are personal, social and universal, and they describe a way of orienting energy in time and space. See Personal Signs and Houses; Social Signs and Houses; Universal Signs and Houses.
Orthogonal Referent—A term used to describe a planet's position north and south of the celestial plane or the plane of the ecliptic. See Plane.
Out of Bounds—Planets that are outside the usual north or south boundaries of the zodiac.
Out-of-Sign—Certain planetary aspects (configurations) coincide with the planets being in specific signs. For example, two planets in conjunction (0°) will generally share the same sign. However, if one planet is 29° Aries and the second planet is 1° Taurus then, although the two planets are in conjunction, they are in different signs and therefore out-of-sign. Also known as a dissociate aspect.