from
The Collaborative International Dictionary of English v.0.48
Incesttuous \In*cest"tu*ous\ (?; 135), a. [L. incestuosus: cf.
F. incestueux.]
1. Guilty of incest; involving, or pertaining to, incest; as,
an incestuous person or connection. --Shak.
[1913 Webster]
Ere you reach to this incestuous love,
You must divine and human rights remove. --Dryden.
2. resembling incest; between people or groups so closely
related as to make such activity improper or unethical;
as, an incestuous coziness between the management of the
company and its union; an incestuous relationship between
the salesman and the purchasing manager.
[PJC] -- {In*cest"tu*ous*ly}, adv. --
{In*cest"tu*ous*ness}, n.
[1913 Webster]