Derma is a derivation of the term "Herma." Refers to a hermaphrodite with a slight leaning towards the female gender. Often used in conjunction with the term "herma."
The purposeful filling up of your calendar (usually Outlook calendar) either by yourself or in-the-know coworkers with meaningless appointments so that annoying co-workers can't have access to you.
I completely derma blocked that annoying woman in sales. She can't book squat on my calendar.