| preejection period | The interval between onset of QRS complex and cardiac ejection; electromechanical systole minus ejection time. (05 Mar 2000) |
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| preemption | The act or right of purchasing before others. Specifically: The privilege or prerogative formerly enjoyed by the king of buying provisions for his household in preference to others. The right of an actual settler upon public lands (particularly those of the United States) to purchase a certain portion at a fixed price in preference to all other applicants. Origin: Pref. Pre- + emption: cf. F. Preemption. See Redeem. Source: Websters Dictionary (01 Mar 1998) |
| preen | 1. To dress with, or as with, a preen; to trim or dress with the beak, as the feathers; said of birds. 2. To trim up, as trees. Origin: See Preen,; or cf. Prune. Source: Websters Dictionary (01 Mar 1998) |
| preen gland | A compound alveolar gland of birds located on the dorsum of the tail or pygostyle; the secretion of this gland (fatty acids and wax) exits from a papilla on the dorsal surface at the base of the tail feathers; the bird applies the substance to its feathers by means of the bill when preening. The uropygial gland is lacking in some species but its waterproofing ability is essential to water birds. Synonym: glandula uropygius, oil glands, preen gland. (05 Mar 2000) |
| preepiglottic | Anterior to the epiglottis. (05 Mar 2000) |
| preeruptive | Denoting the stage of an exanthematous disease preceding the eruption. (05 Mar 2000) |
| preexcitation | Premature activation of part of the ventricular myocardium by an impulse that travels by an anomalous path and so avoids physiological delay in the atrioventricular junction; an intrinsic part of the Wolff-Parkinson-White syndrome. (05 Mar 2000) |
| preexcitation syndrome | <syndrome> A form of pre-excitation characterised by a short pr interval and a long qrs interval with a delta wave. (12 Dec 1998) |
| preextraction record | In dentistry, any record made for the purpose of study or treatment planning. See: diagnostic cast. Synonym: preextraction record. (05 Mar 2000) |
| preface | 1. Something spoken as introductory to a discourse, or written as introductory to a book or essay; a proem; an introduction, or series of preliminary remarks. "This superficial tale Is but a preface of her worthy praise." (Shak) "Heaven's high behest no preface needs." (Milton) 2. The prelude or introduction to the canon of the Mass. <engineering> Proper preface, a portion of the communion service, preceding the prayer of consecration, appointed for certain seasons. Synonym: Introduction, preliminary, preamble, proem, prelude, prologue. Origin: F. Preface; cf. Sp. Prefacio, prefacion, It. Prefazio, prefazione; all fr. L. Praefatio, fr. Praefari to speak or say beforehand; prae = before + fari, fatus, to speak. See Fate. Source: Websters Dictionary (01 Mar 1998) |
| prefect | 1. A Roman officer who controlled or superintended a particular command, charge, department, etc.; as, the prefect of the aqueducts; the prefect of a camp, of a fleet, of the city guard, of provisions; the pretorian prefect, who was commander of the troops guarding the emperor's person. 2. A superintendent of a department who has control of its police establishment, together with extensive powers of municipal regulation. 3. In the Greek and Roman Catholic churches, a title of certain dignitaries below the rank of bishop. Apostolic prefect, the head of a mission, not of episcopal rank. Origin: L. Praefectus, fr. Praefectus, p. P. Of praeficere to set over; prae = before + facere = to make: cf. F. Prefet. Source: Websters Dictionary (01 Mar 1998) |
| prefecundation | <physiology> A term collectively applied to the changes or conditions preceding fecundation, especially to the changes which the ovum undergoes before fecundation. Source: Websters Dictionary (01 Mar 1998) |
| preferred direction | <microscopy> Orientation of a specimen as related to a structural or morphological direction, with respect to the polars. (05 Aug 1998) |
| preferred provider organization | A health care delivery model which uses a panel of eligible physicians. (05 Mar 2000) |
| preferred provider organizations | Arrangements negotiated between a third-party payer (often a self-insured company or union trust fund) and a group of health-care providers (hospitals and physicians) who furnish services at lower than usual fees, and, in return, receive prompt payment and an expectation of an increased volume of patients. (12 Dec 1998) |