The segments may be deleted from ALL records  by going to Contacts > Database Management > Attribute Setup > Segmentation

Option 1:

1. Highlight the segment's name
2. Hover over Edit and click Remove
By deleting the segment, it will remove its posting from ALL contacts' records.
*Note.  The segment may need to be recreated for future use

Option 2:

1. Highlight the segment's name
2. Hover over Edit and click Query
3. Create a query with the appropriate values to apply the segment to.  For example, if you do not want the segment to apply to any contact records, your statement could be "last name=ngy5679366bj".  Since no one in your database would meet this criteria, no one would have the segment applied to their contact record.