What is Definition?

Legal Definition
A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories, intensional definitions (which try to give the essence of a term) and extensional definitions (which proceed by listing the objects that a term describes). Another important category of definitions is the class of ostensive definitions, which convey the meaning of a term by pointing out examples. A term may have many different senses and multiple meanings, and thus require multiple definitions.

In mathematics, a definition is used to give a precise meaning to a new term, instead of describing a pre-existing term. Definitions and axioms are the basis on which all of mathematics is constructed.
-- Wikipedia
Legal Definition
Definitions are critical to the operation of the rule of law. Often a legal dispute centers on the meaning of a particular word in a statute, contract, or legal opinion.
Legal Definition
Probable cause and reasonable suspicion are two of the most important concepts in deciding the when it is appropriate for police to make an arrest, search for evidence and stop a person for questioning. Probable cause and reasonable suspicion have evolved through state and federal court decisions, but they began in the U.S. Supreme Court.
Legal Definition
An enumerition of the principal ideas of which a compound idea is formed, to ascertain and explain its nature and character; or it is that which denotes and points out the substance of a thing, to us. Ayliffe's Pand. 59.

2. A definition ought to contain every idea which belongs to the thing defined, and exclude all others.

3. A definition should be, 1st. Universal, that is, such that it will apply equally to all individuals of, the same kind. 2d. Proper, that is, such that it will not apply to any other individual of any other kind. 3d. Clear, that is, without any equivocal, vague, or unknown word. 4th. Short, that is, without any useless word, or any foreign to the idea intended to be defined.

4. Definitions are always dangerous, because it is always difficult to prevent their being inaccurate, or their becoming so; omnis definitio injure civili periculosa est, parum est enim, ut non subvertipossit.

5. All ideas are not susceptible of definitions, and many words cannot be defined. This inability is frequently supplied, in a considerable degree, by descriptions. (q. v.)
-- Bouviers Law Dictionary
Legal Definition
A description of a thing by its properties; an explanation of the 'meaning of a word or term. Webster. The process of stating the exact meaning of a word by means of other words. Worcester. See Warner v. Beers, 23 Wend. (N. Y.) 103; Marvin v. State, 19 Ind. 181; Mickle v. Miles, 1 Grant, Cas. (Pa.) 328. thus, where a lord has a seignory, and lands escheat to him propter defectum sanguinis, but the seisin is withheld from him, this is a deforcement, and the persen who withholds the seisin ls called a "deforceor." 3 Bl. Comm. 172. In Scotch law. The opposition or resistance made to messengers or other public of-ficors while they are actually engaged in the exercise of their offices. Ersk. Inst 4, 4, 32.
-- Black's Law Dictionary