Geometry, the circumference of a circle, ellipsis, or any other regular curvilinear figure.

Periphrasis, or circumlocution (formed from ἀπό, about, and φέρω, I speak), in Rhetoric, a circuitous form of words, much affected by orators, to avoid common and trite modes of expression. The periphrasis is of great use on some occasions; and it is often necessary, to make things be conceived which it is not proper to name. It is sometimes polite to suppress the names, and only to intimate or allude to them. These turns of expression are also particularly serviceable in oratory; for the sublime admitting of no direct citations, there must be a compass taken to insinuate the authors whose authority is borrowed. A periphrasis, by turning round a proper name in order to make it understood, amplifies and raises the discourse; but care must be taken that it be not too much swelled, nor extended mal à propos, in which case it becomes flat and languid.

Peripneumony, Περιπνευμωνία (formed from ἀπό, about, and πνεύσω, lungs), in Medicine, an inflammation of some part of the thorax, properly of the lungs, attended with an acute fever, and a difficulty of breathing.

Perirphanterium, a vessel of stone or brass filled with holy water, with which all those were sprinkled who were admitted by the ancients to their sacrifices. Beyond this vessel no profane person was allowed to pass. We are told by some that it was placed in the adytum, or inmost recess of the temple; but others say that it was placed at the door, which indeed seems to be the most probable opinion. It was used both by Greeks and Romans, and has been evidently borrowed, like many other Pagan ceremonies, by the Church of Rome. The Hebrews had also a vessel for purification.