Before you start
Things you need to know:
This deletes the contacts within your segment. Deleted contacts are moved to the recycle bin for 30 days. After 30 days, their data is permanently removed.
Remove a segment and its contacts from your account
To remove a segment and all of its contacts from your account:
Go to Audience > Segments.
Select the check box for the segment you want to remove.
Expand the MORE ACTIONS menu, and select Remove segment and contacts from account.
Read the warning and select the checkboxes to show you understand.