Found 2 items, similar to Portentously.
English → English (WordNet) Definition: portentously portentously adv : in a portentous manner; “portentously, the engines began to roll”
English → English (gcide) Definition: Portentously 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]