The Collaborative International Dictionary of English v.0.48:

Prescription \Pre*scrip"tion\ (pr[-e]*skr[i^]p"sh[u^]n), n. [F.
   prescription, L. praescriptio, an inscription, preface,
   precept, demurrer, prescription (in sense 3), fr.
   praescribere. See Prescribe.]
   [1913 Webster]
   1. The act of prescribing, directing, or dictating;
      direction; precept; also, that which is prescribed.
      [1913 Webster]

   2. (Med.) A direction of a remedy or of remedies for a
      disease, and the manner of using them; a medical recipe;
      also, a prescribed remedy. Hence: a written order from a
      physician for a medication, which allows a patient to
      legally obtain medication which is required by law to be
      dispensed only on authorization from a physician or other
      qualified medical practitioner.
      [1913 Webster +PJC]

   3. (Law) A prescribing for title; the claim of title to a
      thing by virtue of immemorial use and enjoyment; the right
      or title acquired by possession had during the time and in
      the manner fixed by law. --Bacon.
      [1913 Webster]

            That profound reverence for law and prescription
            which has long been characteristic of Englishmen.
                                                  --Macaulay.
      [1913 Webster]

   Note: Prescription differs from custom, which is a local
         usage, while prescription is personal, annexed to the
         person only. Prescription only extends to incorporeal
         rights, such as a right of way, or of common. What the
         law gives of common rights is not the subject of
         prescription. --Blackstone. --Cruise. --Kent. In Scotch
         law, prescription is employed in the sense in which
         limitation is used in England and America, namely, to
         express that operation of the lapse of time by which
         obligations are extinguished or title protected. --Sir
         T. Craig. --Erskine.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Usucaption \U`su*cap"tion\ (?; 277), n. [L. usucapere,
   usucaptum, to acquire by long use; usu (ablative of usus use)
   + capere to take: cf. usucapio usucaption.] (Roman Law)
   The acquisition of the title or right to property by the
   uninterrupted possession of it for a certain term prescribed
   by law; -- the same as prescription in common law.
   [1913 Webster]

WordNet (r) 3.0 (2006):

prescription
    adj 1: available only with a doctor's written prescription; "a
           prescription drug" [ant: nonprescription(a), over-the-
           counter(a)]
    n 1: directions prescribed beforehand; the action of prescribing
         authoritative rules or directions; "I tried to follow her
         prescription for success"
    2: a drug that is available only with written instructions from
       a doctor or dentist to a pharmacist; "he told the doctor that
       he had been taking his prescription regularly" [syn:
       prescription drug, prescription, prescription medicine,
       ethical drug] [ant: over-the-counter drug, over-the-
       counter medicine]
    3: written instructions for an optician on the lenses for a
       given person
    4: written instructions from a physician or dentist to a
       druggist concerning the form and dosage of a drug to be
       issued to a given patient

Moby Thesaurus II by Grady Ward, 1.0:

205 Moby Thesaurus words for "prescription":
   Procrustean law, act, adverse possession, aid, alodium, alterative,
   analeptic, appurtenance, assistance, authority, balm, balsam, bill,
   birthright, bon ton, boundary, bounds, burgage, bylaw, canon,
   charge, claim, code, colony, command, commission, confinement,
   conformity, conjugal right, consuetude, continence, convention,
   corrective, criterion, cure, custom, de facto, de jure, decree,
   decretum, demand, dependency, derivative title, dictate, dictation,
   direction, directive, discipline, divine right, droit, drug, due,
   edict, enactment, established way, etiquette, faculty, fashion,
   fee fief, fee position, fee simple, fee simple absolute,
   fee simple conditional, fee simple defeasible,
   fee simple determinable, fee tail, feodum, feud, fiefdom, folkway,
   form, formality, formula, formulary, frankalmoign, free socage,
   freehold, gavelkind, general orders, guideline, having title to,
   healing agent, healing quality, help, hold, holding,
   inalienable right, injunction, institute, institution, instruction,
   interest, jus, knight service, law, law of nature, lay fee, lease,
   leasehold, legal claim, legal possession, legislation, lex, limit,
   limitation, mandate, manner, manners, maxim, measure, medicament,
   medication, medicine, moderation, mores, natural right, norm,
   norma, observance, occupancy, occupation, order, order of nature,
   ordinance, ordonnance, original title, owning, possessing,
   possession, power, practice, praxis, precept, preoccupancy,
   preoccupation, preparation, prepossession, prerogative,
   prescribed form, prescript, presumptive right, pretense,
   pretension, principle, proper claim, proper thing, property,
   property right, property rights, proprietary rights, proscription,
   qualification, receipt, recipe, regulation, relief,
   remedial measure, remedy, restorative, restrain, restriction,
   right, ritual, rubric, rule, ruling, seisin, set form, socage,
   social convention, sovereign remedy, specific, specific remedy,
   squatting, standard, standard behavior, standard usage,
   standing custom, standing order, statute, sublease, succor,
   teaching, tenancy, tenantry, tenure, tenure in chivalry,
   time-honored practice, title, tradition, underlease, undertenancy,
   universal law, usage, use, usucapion, vested interest,
   vested right, villein socage, villeinhold, villenage, way,
   what is done, wont, wonting



Bouvier's Law Dictionary, Revised 6th Ed (1856):

PRESCRIPTION. The manner of acquiring property by a long, honest, and
uninterrupted possession or use during the time required by law. The
possession must have been possessio longa, continua, et pacifica, nec sit
ligitima interruptio, long, continued, peaceable, and without lawful
interruption. Domat, Loix Civ. liv. 3, t. 29, s. 1; Bract. 52, 222, 226; Co.
Litt. 113, b; Pour pouvoir prescire, says the Code Civil, 1. 3, t. 20, art.
22, 29, il faut une possession continue et non interrompue, paisible,
publique, et a titre de proprietaire. See Knapp's R. 79.
     2. The law presumes a grant before the time of legal memory when the
party claiming by prescription, or those from whom he holds, have had
adverse or uninterrupted possession of the property or rights claimed by
prescription. This presumption may be a mere fiction, the commencement of
the user being tortious; no prescription can, however, be sustained, which
is not consistent with such a presumption.
     3. Twenty years uninterrupted user of a way is prima facie evidence of
a prescriptive right. 1 Saund. 323, a; 10 East, 476; 2 Br. & Bing. 403;
Cowp. 215; 2 Wils. 53. The subject of prescription are the several kinds of
incorporeal rights. Vide, generally, 2 Chit. Bl. 35, n. 24; Amer. Jurist,
No. 37, p. 96; 17 Vin. Ab. 256; 7 com. Dig. 93; Rutherf. Inst. 63; Co. Litt.
113; 2 Conn. R. 584; 9 conn. R. 162; Bouv. Inst. Index, h.t.
     4. The Civil Code Louisiana, art. 3420, defines a prescription to be a
manner of acquiring property, or of discharging debts, by the effect of
time, and under the conditions regulated by law. For the law relating to
prescription in that state, see Code, art. 8420 to 3521. For the difference
between the meaning of the term prescription as understood by the common
law, and the same term in the civil law, see 1 Bro. Civ. Law, 246.
     5. The prescription which has the effect to liberate a creditor, is a
mere bar which the debtor may oppose to the creditor, who has neglected to
exercise his rights, or procured them to be acknowledged during the time
prescribed by law. The debtor acquires this right without any act on his
part, it results entirely from the negligence of the creditor. The
prescription does not extinguish the debt, it merely places a bar in the
hands of the debtor, which he may use or not at his choice against the
creditor. The debtor may therefore abandon this defence, which has been
acquired by mere lapse of time, either by paying the debt, or acknowledging
it. If he pay it, he cannot recover back the money so paid, and if he
acknowledge it, he may be constrained to pay it. Poth. Intr. au titre xiv.
des Prescriptions, Bect. 2. Vide Bouv. Inst. Theo. pars prima, c. 1, art. 1,
Sec. 4, s. 3; Limitations.



The Devil's Dictionary (1881-1906):

PRESCRIPTION, n.  A physician's guess at what will best prolong the
situation with least harm to the patient.