Definition of semimajor axis
: one half of the major axis of an ellipse (as that formed by the orbit of a planet)
First Known Use of semimajor axis
Learn More about semimajor axis
Britannica.com: Encyclopedia article about semimajor axis
Seen and Heard
What made you want to look up semimajor axis? Please tell us where you read or heard it (including the quote, if possible).