interplanetary
Interplanetary (adj) means existing or occurring between planets. Example: “The agency is planning an interplanetary mission to Mars.”
How to use interplanetary
Learner’s notesIn plain EnglishRelating to travel or activity that happens between planets, rather than within one solar system's single world.
Fill the gap
Can you complete this real example?
The agency is planning an _____ mission to Mars.
Etymology
From inter- ("between") plus planetary.