A female who is a cunt without question, but goes a step beyond mere cunthood by simultaneously being as annoying as a mosquito - typically by complaining about pretty much everything. A cuntskeeto's inane whining may even come to resemble the mosquito's high-pitched buzz, hence the term.
A cuntskeeto further resembles a mosquito in that she always seems to hover around you and your friends despite your best efforts to shoo her away, she yearns to mate with all males in the immediate vicinity (no matter the time, location, or context), and she tends to drain the lifeblood from any social gathering.
"No offense, dude, but your ex-girlfriend is a cuntskeeto."
"I know, man. It was such bad luck running into her last night. I'm really sorry she ruined our good time. But as soon as she finds anyone having fun without her, she latches on and sucks out as much enjoyment as she can until she's bloated with our stolen happiness."
"Or until she has something else to suck?"
"That's gross, man. She has syphilis."