Definition of 3D:
(n) :
thruppence, threepence, a coin valuing three pennies
(n) :
(science fiction) A three-dimensional video.
(n) :
(science fiction) A system capable of recording or displaying three-dimensional video.
(adj) :
Abbreviation of three-dimensional. [(not comparable) Existing in three dimensions.]
(adj) :
Obsolete form of 3rd.