The Collaborative International Dictionary
Longtail \Long"tail`\, n. An animal, particularly a log, having an uncut tail. Cf. Curtail. Dog.
Note: A longtail was a gentleman's dog, or the dog of one qualified to bunt, other dogs being required to have their tails cut.
Cut and longtail, all, gentlefolks and others, as they
might come.
--Shak.
Wiktionary
n. 1 A common designation for an animal that has an unusually long tail relative to similar species. 2 In Bermuda, an alternative name for the white-tailed tropicbird. 3 A longtail boat. 4 (context colloquial English) In the Isle of Man, a rat.
WordNet
Wikipedia
On the Isle of Man, longtail is a euphemism used to denote a rat, as a relatively modern superstition has arisen that it is considered bad luck to mention this word. The origins of this superstition date to sea- taboos, where certain words and practices were not mentioned aboard ship, for fear of attracting bad luck (or bad weather).
The Manx Gaelic author Edward Faragher (also known by his Manx nickname 'Ned Beg Hom Ruy') recorded in his work 'Skeealyn 'sy Ghailck' that during his time working on fishing boats in the 19th century "It was forbidden to name a hare on board, or a rabbit, or a rat or a cat. The hare was 'the big-eared fellow', and the rabbit ‘pomet’, and the rat ‘sacote’, and the cat ‘scratcher'". In the modern superstition, the taboo only applies to the rat, and the term 'sacote' is no longer used.
Although this particular sea-taboo was one amongst many and was not held to apply on land, it has become a popular modern belief that the word is somehow unlucky and the taboo has been adopted by some as a typical Manx practice, despite the fact that the old Manx had no qualms in using the word, or its Manx equivalent, "roddan". In modern times, even non-local and unsuperstitious people will refrain from using the word "rat" perhaps in an effort to fit in with those who take it seriously, or in an attempt to be folksy.
Local socially acceptable alternatives for the superstitious also include joey, ringie, queerfella, iron fella and . Recently young people have also begun saying r-a-t, owing to the influence of English immigrants.
Similar taboos can be found as far north as Shetland. Other sea taboos included pigs, cats, and knives. There is a comparable and apparently also relatively modern taboo against uttering the word 'rabbit' on the Isle of Portland.
Usage examples of "longtail".
Jollie Longtail, the nice little mousie boy, about whom I once told you.
Jollie and Jillie Longtail, you know, and she has been ill with mouse-trap fever.
A pogue taken from a dizzy shop-girl containing one silver shilling carried the same penalty at law as a dumby lifted from a rich toff stuffed with Bank of England longtails and jingling with gold sovereigns.
He then took up the notes, several thousand pounds of counterfeit longtails, which he placed in the grate and set alight, setting fire to the pile three times in all to make certain that there was nothing left but a handful of ashes.
He, on the other hand, had changed his buckskins and frockcoat for pantaloons and a longtailed coat of fine blue cloth, and had arranged a fresh necktie in intricate folds about his throat.
She walks back to the house, taking her time, watching the little longtailed garter-striped lizards whisk off the sunny spots in the lane and out of her way.
I had gone back and made them all into vampires, and there we were, the House de Lioncourt, whitefaced beauties even to the bloodsucking baby that lay in the cradle and the mother who bent to give it the wriggling longtailed gray rat upon which it was to feed.