from
The Collaborative International Dictionary of English v.0.48
Portentous \Por*tent"ous\, a. [L. portentosus.]
1. Of the nature of a portent; containing portents;
foreshadowing, esp. foreshadowing ill; ominous.
[1913 Webster]
For, I believe, they are portentous things. --Shak.
[1913 Webster]
Victories of strange and almost portentous splendor.
--Macaulay.
[1913 Webster]
2. Hence: Monstrous; prodigious; wonderful; dreadful; as, a
beast of portentous size. --Roscommon.
[1913 Webster] -- {Por*tent"ous*ly}, adv. --
{Por*tent"ous*ness}, n.
[1913 Webster]