DEFILE, a military expression for a passage, to march through which troops are compelled to "defile," or narrow their front (from the Fr. _défiler_, to march in a line, or by "files"). The word is usually applied to a ravine or gorge in a range of hills, but a causeway over a river, a bridge and even a village may equally be called a defile. The term is also used to express, without any special reference to military operations, a gorge in mountains. The verb "to defile" is used of troops marching on a narrow front, or narrowing their front, under all circumstances, and in this sense is the contrary of "deploy."
"Defile," in the sense of "pollute," is another form of "defoul"; though spelt alike, the two words are pronounced differently, the accent being on the first syllable for the former and on the second for the latter.
DEFINITION (Lat. _definitio_, from _de-finire_, to set limits to, describe), a logical term used popularly for the process of explaining, or giving the meaning of, a word, and also in the concrete for the proposition or statement in which that explanation is expressed. In logic, definition consists in determining the qualities which belong to given concepts or universals; it is not concerned with individuals, which are marked by an infinity of peculiarities, any one or all of which might be predicated of another individual. Individuals can be defined only in so far as they belong to a single kind. According to Aristotle, definition is the statement of the essence of a concept ([Greek: horismos men gar tou ti esti kai ousias], _Posterior Analytics_, B iii. 90 b 30); that is, it consists of the genus and the differentia. In other words, "man" is defined as "animal _plus_ rationality," or "rational animal,"[1] i.e. the concept is (1) referred to the next higher genus, and (2) distinguished from other modes in which that genus exists, i.e. from other species. It is sometimes argued that, there being no definition of individuals as such, definition is of names (see J. S. Mill, _Logic_, i. viii. 5), not of things; it is generally, however, maintained that definition is _of things, regarded as, or in so far as they are, of a kind_. Definition of words can be nothing more than the explanation of terms such as is given in a dictionary.