Jack-in-a-box

Jack-in-a-box
  1. A tropical tree (Hernandia sonora), which bears a drupe that rattles when dry in the inflated calyx. (Bot.)
  2. A child's toy, consisting of a box, out of which, when the lid is raised, a figure (usually a clown) springs; also called jack-in-the-box.
  3. An epicyclic train of bevel gears for transmitting rotary motion to two parts in such a manner that their relative rotation may be variable; applied to driving the wheels of tricycles, road locomotives, and to cotton machinery, etc.; an equation box; a jack frame; -- called also compensating gearing. (Mech.)
  4. A large wooden screw turning in a nut attached to the crosspiece of a rude press.