A planet that orbits the Sun within the orbit of the Earth, and thus does not show retrograde motion when viewed from Earth

(anatomy) Ellipsis of inferior oblique muscle.

(anatomy) One of the four extraocular muscles of the eyeball in the orbit, which arises from the border of the optic foramen and inserts into the inferior aspect of the sclera.

(psychology) A sense of inferiority; the feeling that one is inferior to others in certain aspects.

(economics) a good that decreases in demand when consumer income rises; having a negative income elasticity of demand.

(dated) An explosive device designed to cause damage to life or property.

plural of infernal machine

(obsolete) lapis infernalis, lunar caustic / (obsolete) caustic potash

(historical) A time bomb.

plural of infernal device