1. On duty or ready to be put on duty by a naval or military service; in active service.
The old battleship has been in commission for twenty years.
It took many months to build the new bomber, and now it is ready to be put into commission.
2. In proper condition; in use or ready for use; working; running.
The wheel of my bicycle was broken, but it is back in commission now.
Compare: IN ORDER (2).
Contrast: OUT OF COMMISSION (2).