syzygy

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Astronomy Either of two points in the orbit of a celestial body where the body is in opposition to or in conjunction with the sun.
2. n. Astronomy Either of two points in the orbit of the moon when the moon lies in a straight line with the sun and Earth.
3. n. Astronomy The configuration of the sun, the moon, and Earth lying in a straight line.
4. n. The combining of two feet into a single metrical unit in classical prosody.

Century Dictionary and Cyclopedia

1. n. In astronomy, the conjunction or opposition of a planet with the sun, or of any two of the heavenly bodies. On the phenomena and circumstances of the syzygies depends a great part of the lunar theory.
2. n. In ancient prosody, a group or combination of two feet. Ancient metricians varied in their use of this term. Some use it regularly for a dipody or (dipodic) measure. Others call a tautopody, or double foot, a dipody, but a combination of two different feet a syzygy. Some, accordingly, giving the name syzygy to tetrasyllabic feet (regarded by them as composed of two dissyllabic feet), speak of an iambic or a trochaic line as measured by dipodies, but an Ionic line as measured by syzygies—that is, by single Ionics considered as combinations of trochees and pyrrhics. A peculiar use is the restriction of the term syzygy to compound feet of five or six syllables.
3. n. In algebra, a linear function in the variables. See syzygetic.
4. n. In zoology, the conjunction of two organs or organisms by close adhesion and partial concrescence, without loss of their identity; also, the thing so formed, or the resulting conformation; a syzygium: a term variously applied. Zygosis or conjugation, as observed in various protozoans and other low organisms. See conjugation, 4, Diplozoön, and diporpa.

Wiktionary

1. n. A kind of unity, namely an alignment of three celestial bodies (for example, the Sun, Earth, and Moon) such that one body is directly between the other two, such as occurs at an eclipse
2. n. An archetypal pairing of contrasexual opposites, symbolizing the communication of the conscious and unconscious minds
3. n. A relation between generators of a module
4. n. The fusion of some or all of the organs
5. n. The association of two protozoa end-to-end or laterally for the purpose of asexual exchange of genetic material
6. n. The pairing of chromosomes in meiosis

GNU Webster's 1913

1. n. The point of an orbit, as of the moon or a planet, at which it is in conjunction or opposition; -- commonly used in the plural.
2. n. The coupling together of different feet.
3. n. Any one of the segments of an arm of a crinoid composed of two joints so closely united that the line of union is obliterated on the outer, though visible on the inner, side.
4. n. The immovable union of two joints of a crinoidal arm.
5. n. The intimately united and apparently fused condition of certain low organisms during conjugation.

WordNet 3.0

1. n. the straight line configuration of 3 celestial bodies (as the sun and earth and moon) in a gravitational system