Definition of LEM:
(n) :
(US, space science) Originally Lunar Excursion Module, latterly Lunar Module.
(n) :
(logic) Law of excluded middle.
(n) :
A surname.
(n) :
(informal) Clipping of Leamington Spa. [A spa town in Royal Leamington Spa parish, Warwick district, Warwickshire, England, also known as Royal Leamington Spa or just Leamington (OS grid ref SP3165).]