Jack-in-a-box


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1.(Bot.) A tropical tree (Hernandia sonora), which bears a drupe that rattles when dry in the inflated calyx.
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.(Mech.) 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.
4.A large wooden screw turning in a nut attached to the crosspiece of a rude press.