To cancel a meeting, open the calendar entry and click on the Remove Event from Calendar button. A notice will be sent to all invitees letting them know the meeting was cancelled.
To remove an invitee from a calendar entry:
Click once on the calendar entry to open it.
Select the Edit button.
Remove the name from the To, Cc or Bcc field
Select the Save button.
A notice will be sent to all invitees that were removed from the calendar entry canceling the meeting.