Kinktionary
More like guidelines and a lot less like definitions.
Dragon
Similar to Centaur/Pegasus except that the Dragon usually requires to be recognized as the dominant male in the activity or relationship. They often take on a more Bull/cuckold role but may also dominate the male sexually as well as the female.
A Wyrmling is a different version of a Dragon. They can take on a more dominant role with the couple but don’t demand or require that role to participate.
In some communities people may also use Dragon as a polyamorous term for the male version of a unicorn without any connotations of dominance.