Definitions

1. adjective

relating to or being the larger of two axes in an ellipse or other closed curve, the axis that is farther from the center.

“The semimajor axis of the comet’s orbit is approximately 10 astronomical units from the sun.”

2. noun

the semimajor axis of an ellipse or other closed curve, especially in astronomy.

“The semimajor of the planet’s orbit was a crucial piece of information in determining its trajectory.”