An very attractive and enticingly sexy woman.
Possibly derived from Firecracker or Crackerjack. The word visually describes how an such a woman excites a man's mind, emotions and passions.
Sadly, this wonderfully expressive word is under threat due to the rise of alternative meanings.
She's a beauty - real cracker!", he exclaimed passionately. "I felt like all firecrackers and champagne corks in the world were whizzing, crackling and popping at once.