What is gaavad?

Some articles on gaavad:

Edah Ha Chareidis - Rabbinical Court
... headed by both a Chief Rabbi called the "Gaavad" גאב"ד, and by the Head of Rabbinical Court called a "Raavad" ראב"ד ... The "Raavad" is the first person in the line of succession of the "Gaavad", and would usually ascend to the role of "Gaavad" upon his death or resignation ...