noun. An unholy-ish union of chihuahua and rat terrier. Or a chihuahua and rat. Yum!
Related terms: poodlehuahua, pughuahua, wienerhuahua.
Real citation: “It's COLD outside, especially if you're a little rat terrier/chihuahua (i.e. 'rathuahua') with super short hair and you've already outgrown your adoption-day sweater. No problem staying warm inside the house, though!”
(Angela Pratt, Dec. 15, 2004, http://sacgardening.blogspot.com/2004/12/poor-puppies.html)
Made-up citation: "Our new selection of rathuahuas, roach-huahuas, and protozoahuahuas will dazzle the eye, pull the heartstrings, and almost fill the purse."