eject -- Eject the removable media

Eject allows removable media (like CD-ROM, Floppy, Tape, JAZ, ZIP) to
be ejected under software control. The command can also control some
multi-disc CD-ROM changers, the auto-eject feature supported by some
devices, and close the disc tray of some CD-ROM drives.

Examples:

$ eject -- Eject the default device, mostly CD.

$ eject -v -- Same as above and show more info.

$ eject /dev/cdrom -- Eject CD using device file name.

$ eject -t -- Close the drive tray.

$ eject -vt -- Same as above and show more info.

Read: man eject