This is an irregular feature - both in frequency and oddness - dedicated to a word I came across that I have never previously used.
aeolipile (ay-OH-lih-pile) n. first steam engine, described in 1st century CE, featuring a globe made to revolve by pressure from steam jets; an instrument used to determine the force at which heated vapour escapes from a vessel through a narrow opening.
Also spelled aeolipyle or eolipile, the term is derived from the Latin Aeolus ("god of the winds") and pila ("ball"). The aeolipile, believed to have been created in the first century by Hero of Alexandria, is considered to be the first working steam engine.
Left: illustration of Hero's aeolipile
Hero's aeolipile was a hollow sphere mounted in such a way that it could rotate on a pair of hollow tubes that provided steam to the sphere from a heated water kettle. The water vapor escaped from two L-shaped tubes on opposite sides of the sphere that projected from its equator. The escaping gas gave thrust to the sphere, which then caused it to rotate.
If only Hero could have applied this technology to ceiling fans, he might then have been the first inventor of air conditioning.