Meaning of midcourse

mid•course

Pronunciation: (mid'kôrs", -kōrs"), [key]
— n.
  1. the middle of a course.
  2. the portion of a ballistic trajectory between the end of powered flight and the beginning of the reentry phase.
  3. the portion of a space trajectory between leaving the earth's vicinity and arrival at the desired destination, as another planet.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.