noun

• (Roman Catholicism, also figurative) A small, usually round container used to hold the host (“consecrated bread or wafer of the Eucharist”), especially when bringing communion to the sick or others unable to attend Mass.
  "[F]oraſmuche as we have often and many tymes, to our inwarde regrete and diſpleaſure, ſeen at oure Jen, in diverſe and many Churches of our Realme, the holie Sacrament of the Aulter kept in ful simple and inhoneſt Pixes, ſpecially Pixes of copre and tymbre: we have appointed and commaunded the Treſourer of our Chambre, and Maiſtre of our Juellhouſe, to cauſe to be made furthwith Pixes of ſilver and gilte, in a greate nombre, for the keping of the holie Sacrament of th'Aultre, after the faction of a Pixe that we have cauſed to be delivered to theim, […]"
• (by extension, rare) A (small) box; a casket, a coffret.
  "It is not Beauty, which its Bluſh doth owe / Unto the Pixe and Pencill."
• (chiefly British) A box used in a mint as a place to deposit sample coins intended to have the fineness of their metal and their weight tested before the coins are issued to the public.
  "[T]he said Tresurer and other Officers of the sayd Mynts, to bring with them, at that tyme and place, all ther Pixes, and ther severall Indentures of Coynag, by and for the holle tyme the said Assaye shall be taken."
• (nautical, obsolete, rare) A compass used by sailors.
  "Here I lament I had not the accomodation^([sic]) of the Pyxis, or any Horizontal Plate divided into more points of the Compaſs, though I ſee not that Natural Knowledge requires ſo exact a Pyx as Navigation uſeth; becauſe I boggle at this, that I find the North Cardinal point gives more inſtances than the Weſt."

verb

• (obsolete) To place (the host) in a pyx.
  "Than was yt boxed pyxed and tabernacled & so borne forth in processyon with torche lyght banner crosse candelstyck."
• (figuratively) To enclose (something) in a box or other container; specifically, to place (a deceased person's body) in a coffin; to coffin, to encoffin.
  "Here lies poor Artedi, in foreign land pyx'd / Not a man nor a fish, but something betwixt, / Not a man, for his life amongst fishes he past, / Not a fish, for he perished by water at last."
• (chiefly British) To deposit (sample coins) in a pyx; (by extension) to test (such coins) for the fineness of metal and weight before a mint issues them to the public.
  "After the said moneys shall be by the said warden and the assaymaster tried and pyxed as ordered by the said indenture, the said master worker shall make true deliverance and payment of the same to every person by weight by the same balance and weight whereof he shall receive the same bullion, taking again his said bills; […]"