Doofus laugh
This is a chuckle that sounds like the way a bobble-head doll would laugh after being tweaked. It has a certain amount of Mortimer Snerd in it. When the doofus executes this laugh correctly, said doofus will tend to drool on himself and possibly others. This is not a problem unless the entity who is drooled upon is a carrier of the Doofus gene. What happens then, you don't even want to know. But because this is a dictionary, I have to tell you.
A genetic match of drool and fool results in reverse cool. It's not a pretty sight. For example, the doofusse's (or Doofigh's) very existence can implode. In this implosion one can break out into slobbering tears like Rep. John Boehner did recently. That was a fine example of a Doofus laugh "gone south AND sissy."