adv

• (historical, calligraphy, of writing) In a fashion such that the reading direction changes from right-to-left to left-to-right with each new line.

adj

• (historical, calligraphy, of writing) Written from right-to-left and left-to-right on alternate lines.
• (figuratively) Changing direction, going back and forth.

noun

• (historical, calligraphy, of writing) Writing that is right-to-left and left-to-right on alternate lines.
  "The number of Attic boustrophedon texts is fairly small; most of those just cited have been brought down by the experts to a date close to 550 B.C., a date to which several texts of more than one line inscribed left to right may also be assigned (cf. pp.56—57 infra), besides the four-line retrograde sep. mon. of Pediarchus cited in the previous section (cf. p.52 supra). Stone texts only really become numerous in Attica about 550, and by this time it is clear that left-to-right writing is just as common as boustrophedon, and may have been so even earlier.[…]After 540 boustrophedon was certainly unusual."