Source : Webster's Revised Unabridged Dictionary (1913)
Treacherous \Treach"er*ous\, a. [See {Treacher}.]
Like a traitor; involving treachery; violating allegiance or
faith pledged; traitorous to the state or sovereign;
perfidious in private life; betraying a trust; faithless.
Loyal father of a treacherous son. --Shak.
The treacherous smile, a mask for secret hate.
--Cowper.
Syn: Faithless; perfidious; traitorous; false; insidious;
plotting. -- {Treach"er*ous*ly}, adv. --
{Treach"er*ous*ness}, n.