noun

• (archaic) Someone engaged in teaching the alphabet; an elementary teacher; one that teaches the methods and principles of learning.
• (rhetoric) A work which uses words or lines in alphabetical order.
  "This formal organization is most likely to create obscurity in such elaborate and artificial forms as: palindromes (words, phrases, or verses which read the same backward or forward), abecedarians (poems in which the initial letters of lines or stanzas are arranged to[…])[…]."

adj

• (now rare) Pertaining to someone learning the alphabet or basic studies; elementary; rudimentary.

noun

• (historical) A member of a 16th-century Anabaptist sect, follower of the Zwickau prophets (and specially of Thomas Storch), who believed that any kind of knowledge (even basic reading and writing) would keep one from obtaining salvation.
  "Behind the stable doors, where competitors frenziedly shine tack and polish hooves, Donna McNulty busies herself with her horse, Abecedarian."