From WordNet (r) 2.0 (August 2003) [wn]:
cad
n 1: someone who is morally reprehensible; "you dirty dog" [syn:
bounder, blackguard, dog, hound, heel]
2: software used in art and architecture and engineering and
manufacturing to assist in precision drawing [syn:
computer-aided design, CAD]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Cad \Cad\, n. [Abbrev. fr. cadet.]
1. A person who stands at the door of an omnibus to open and
shut it, and to receive fares; an idle hanger-on about
innyards. [Eng.] --Dickens.
[1913 Webster]
2. A lowbred, presuming person; a mean, vulgar fellow. [Cant]
--Thackeray.
[1913 Webster]
From The Free On-line Dictionary of Computing (19 Sep 2003) [foldoc]:
CAD
Computer Aided Design