The planet which is lord of the sign where another planet is.
The planet that rules the sign or dignity another planet occupies. For example, if Mars is in Libra, the dispositor of Mars is Venus.
The dispositor of a planet is the ruler of the sign in which the planet is placed. Example: If the Moon is in the sign of Leo then the Sun (which is the ruler of Leo) is the Moon's dispositor. However, an exception to this rule can be found if the Almuten of a planet is calculated. For example, if Saturn is at 18°AR45' the Almuten of that longitude is the Sun, not Mars, which means the Sun becomes Saturn's dispositor.
When a planet is in the sign ruled by another, that planet is said to be disposed of by the ruler, its dispositor. For example, Mars in Sagittarius in said to be disposed of by Jupiter, the ruler of that sign. Jupiter is thus the dispositor of Mars. Disposition by a benefic is favourable and especially so if the dispositor is elevated or more elevated than the disposed. Mutual Disposition (when planets are in each other's signs, eg: Moon in Leo and Sun in Cancer) is very favourable and reduces any surrounding negativity. Disposition is particularly important in Horary readings.
The planet that rules the sign another planet occupies. For example, Mercury in Taurus is disposited by Venus, the natural planetary ruler of Taurus. A dispositor influences the action of the planet it disposits.
In astrology, a dispositor is a planet or celestial body that is the natural ruler of a sign that another planet is posited in. The dispositor tends to have an influence on how the planet posited in the sign operates.