Aphraktos. Undeckted Grecian ship of classic times.
Aplanatic. In optics, means 'without aberration'. Used when spherical and chromatic aberrations have been eliminated.
Aplanatic Refraction. Refraction that has been corrected for spherical aberrations. Apogean Range.Mean minimum range of an apogean tide; usually about 0-8 of mean tide. Apogean Tide. Tidal undulation occurring about time of Moon being in apogee. Increase in Moon's distance from Earth reduces her gravitational and tractive efforts. Apogee. Point in Moon's orbit that is farthest from Earth.