1. backstairs a second staircase at the rear of a building
  2. backstop a structure to prevent a ball from traveling out of a field
  3. juxtaposition the act of positioning close together
  4. bookstore a shop where books are sold
  5. bookstall a shop where books are sold
  6. backspace the typewriter key used for back spacing
  7. juxtapose place side by side
  8. postpose place after another constituent in the sentence
  9. lockstep a manner of marching in file in which each person's leg moves with and behind the corresponding leg of the person ahead
  10. boost up push upward
  11. book of maps a collection of maps in book form
  12. Pick's disease a progressive form of presenile dementia found most often in middle-aged and elderly women and characterized by degeneration of the frontal and temporal lobes with loss of intellectual ability and transitory aphasia
  13. pogo stick plaything consisting of a pole with foot rests and a strong spring; propelled by jumping
  14. backstage a stage area out of sight of the audience
  15. backstitch an overlapping stitch made by starting the next stitch at the middle of the preceding one
  16. big stick a display of force or power
  17. Bemisia tabaci a strain of pest accidentally imported into Florida from the Middle East then spread to California where it is a very serious pest feeding on almost all vegetable crops and poinsettias
  18. backstair secret and sly or sordid
  19. backspin spin that retards or reverses the forward motion
  20. box tortoise chiefly terrestrial turtle of North America