1. Morally binding or necessary
   "it is incumbent on me to attend"

See also: irremissible, obligatory

• spontaneity
• spontaneous
• spontaneous abortion
• spontaneous combustion
• spontaneous generation
• spontaneously
• spontaneousness
• spontoon
• spoof
• spook
• spookily
• spooky
• spool
• spooler
• spoon
• spoon bread
• spoon food
• spoon-shaped
• spoonbill
• spoonbill catfish
• spoondrift
• spoonerism
• spoonfeed
• spoonfeeding
• spoonflower