equatorial

American Heritage® Dictionary of the English Language, Fourth Edition

1. adj. Of, relating to, or resembling the earth's equator.
2. adj. Relating to conditions that exist at the earth's equator: equatorial heat.
3. adj. Having or constituting a support with two perpendicular axes, one of which is parallel to the earth's rotational axis.
4. n. An equatorial telescope.

Century Dictionary and Cyclopedia

1. Of or pertaining to the equator: as, equatorial climates; the equatorial diameter of the earth is longer than the polar diameter.
2. n. An astronomical instrument contrived for the purpose of directing a telescope upon any celestial object of which the right ascension and declination are known, and of keeping the object in view for any length of time notwithstanding the diurnal motion. For these purposes a principal axis resting on firm supports is placed parallel to the axis of the earth's rotation, and consequently pointing to the poles of the heavens. On this polar axis there is placed, usually near one of its extremities, a graduated circle, the plane of which is perpendicular to the polar axis, and therefore parallel to the equator. This circle is called the equatorial circle, and measures by its arcs the hour-angles, or differences of right ascension. The polar axis carries a second circle, called the declination circle, the plane of which is at right angles to that of the equatorial circle. This last circle has a telescope attached to it for making observations, which moves along with it in the same plane. The name equatorial, or equatorial instrument, is sometimes given to any astronomical instrument which has its principal axis of rotation parallel to the axis of the earth.
3. In crystallog., of or pertaining to the horizontal or lateral plane.

Wiktionary

1. adj. of, near, or relating to the equator
2. n. astronomy A kind of telescope mounted so as to have two axes of motion at right angles to each other, one of them parallel to the axis of the Earth, and each carrying a graduated circle, one for measuring declination, and the other right ascension, or the hour angle, so that the telescope may be directed, even in the daytime, to any star or other object whose right ascension and declination are known.

GNU Webster's 1913

1. adj. Of or pertaining to the equator; ; also, pertaining to an equatorial instrument.
2. n. (Astron.) An instrument consisting of a telescope so mounted as to have two axes of motion at right angles to each other, one of them parallel to the axis of the earth, and each carrying a graduated circle, the one for measuring declination, and the other right ascension, or the hour angle, so that the telescope may be directed, even in the daytime, to any star or other object whose right ascension and declination are known. The motion in right ascension is sometimes communicated by clockwork, so as to keep the object constantly in the field of the telescope. Called also an equatorial telescope.

WordNet 3.0

1. adj. of or relating to conditions at the geographical equator
2. adj. of or existing at or near the geographic equator
3. adj. of or relating to or at an equator
4. n. a telescope whose mounting has only two axes of motion, one parallel to the Earth's axis and the other one at right angles to it