Definition of simplex:
(adj) :
(computing, telecommunications) Of a circuit or device: involving signals which travel in one direction at a time; unidirectional.
(adj) :
(linguistics) Of a word: having no (derivational) affixes; simple, monomorphemic, uncompounded.
(n) :
(linguistics) A word which is not compound and contains no derivational affixes (inflectional affixes are usually disregarded); a monomorphemic word.
(adj) :
(originally and chiefly US) Of an apartment (or, sometimes, another type of property): having only one floor or storey; single-storey.
(n) :
(originally and chiefly US) An apartment (or, sometimes, another type of property) having only one floor or storey; a single-storey property.
(adj) :
(dated) Having a single structure; not composite or complex; undivided, unitary.