incumbent in WordNet English dictionary

1. the official who holds an office
   incumbent  officeholder 
   

1. currently holding an office
   "the incumbent governor"
   incumbent 
   
2. necessary (for someone) as a duty or responsibility; morally binding
   "it is incumbent on them to pay their own debts"
   incumbent 
   
3. lying or leaning on something else
   "an incumbent geological formation"
   incumbent