noun

• (historical) A small shield, especially one of an approximately elliptical form, or crescent-shaped.
  "Xenophon also mentions bronze peltae, but probably (like hoplite shields) they were only faced with a thin covering of bronze."
• (art, historical) A crescent-shaped design used in mosaics.
  "A pattern of red and blue peltae on a white ground, arranged in groups of four with two peltae placed back to back and one at each end facing inward, forms the outer border on the east side of the mosaic."
• (botany) A flat apothecium with no rim.
  "The calyx is composed of five linear spreading sepals J inch long and attached to the sides of the inferior ovary are four bracts, two of which, the anterior and posterior, remain abortive, whilst the two lateral ones develop into large rounded flattened discs (peltae) attached at the centre."
• (microbiology) A crescent-shaped sheet of microtubules that encircles the base of the flagella of a protozoan.
  "A striated parabasal fibre is closely associated with a large parabasal golgi system; a dense pre-axostylar fibre connects to the axostyle, which is a curved sheet of microtubules that encloses the nucleus and extends to (or protrudes from) the posterior end of the cell; the same pre-axostylar fibre links to the pelta, which is a sheet of microtubules that curves around within a sort of collar that encloses the flagellar bases before turning back to meet the axostyle […]"