sorites

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An argument presenting a series of premises that can be analyzed as a chain of syllogisms, with each syllogism's major term forming the minor term of the next, until a final conclusion is attained. For example, a sorites might consist of the premises that some pets are snakes, that no snakes have fur, and that only furry things are cuddly, yielding the conclusion that not all pets are cuddly.
• noun An argument exploiting the imprecision of everyday language to reach a paradoxical conclusion. The classic argument of this sort maintains that one grain of sand does not make a heap and that adding a single grain of sand to something that is not a heap does not make a heap, yielding the conclusion that no additional amount of sand can make a heap.
• adjective Of or relating to a sorites.

from The Century Dictionary.

• noun A kind of sophism invented by Chrysippus in the third century before Christ, by which a parson is led by gradual steps from maintaining what is manifestly true to admitting what is manifestly false.
• noun A chain-syllogism, or argument having a number of premises and one conclusion, the argumentation being capable of analysis into a number of syllogisms, the conclusion of each of which is a premise of the next.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Logic) An abridged form of stating of syllogisms in a series of propositions so arranged that the predicate of each one that precedes forms the subject of each one that follows, and the conclusion unites the subject of the first proposition with the predicate of the last proposition.
• noun See under Destructive.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun logic, rhetoric A series of propositions whereby each conclusion is taken as the subject of the next.