noun

• (pathology, usually uncountable) A disorder characterized by appetite and craving for non-edible substances, such as chalk, clay, dirt, ice, or sand.
  "The three most common nonfood picas were eating of strings and rags; feces, vomit, and urine; and paper, cigarettes, and soil."
• (countable) A magpie.

noun

• (typography, printing, uncountable) A size of type between small pica and English, now standardized as 12-point.
  "I had been at Baldwin's before dinner in consequence of a letter from him which showed me that, by using a pica instead of an English letter in printing my book, I might comprise it within such a number of sheets as a guinea-volume should contain […]."
• (typography, uncountable, usually with qualifier) A font of this size.
• (typography, countable) A unit of length equivalent to 12 points, officially ³⁵⁄₈₃ cm (0.166 in) after 1886 but now (computing) ¹⁄₆ in.
• (uncommon, ecclesiastical) A pie or directory: the book directing Roman Catholic observance of saints' days and other feasts under various calendars.

noun

• (space flight) Abbreviation of phenolic impregnated carbon ablator.
• (anatomy) Initialism of posterior inferior cerebellar artery.