Adjective
(geometry) Of or pertaining to the semimajor axis, the long axis of an ellipse
a semimajor radius
Less than major, but still significant
Source: en.wiktionary.orgHere P is the time taken for a planet to complete an orbit round the sun, and a is the mean value between the maximum and minimum distances between the planet and sun (i.e. the semimajor axis). Source: Internet
Web calculator that plots distributions of the semimajor axes (or in one case the perihelion distances) of the minor planets in relation to mean-motion resonances of the planets (website maintained by M.A. Murison). Source: Internet
This yields numerical values for the Moon's secular deceleration, i.e. negative acceleration, in longitude and the rate of change of the semimajor axis of the Earth–Moon ellipse. Source: Internet