1. a loud-voiced, ill-tempered scolding women; a shrew.
2. Archaic. a woman of strength and spirit
Synonyms - scold, nag, termagant, harpy, Xanthippe.
Note that there are no synonyms listed for the second definition (and see the linked word for more synonyms). I suspect that this is probably because the second definition, identified as archaic, is no longer used (by the way, the 2002 Oxford American college dictionary, also identifies the second definition as archaic, but is slightly different: "a woman of masculine strength or spirit; a female warrior" [emphasis mine]), but I have to say other than maybe "amazon" I can't really think of a synonym for the "woman of strength or spirit" definition.
So I looked up amazon to see if dictionary.com would lead me to any interesting synonyms. Amazon pops up in the synonym lists for "women" and for "mean lady." The synonym list for women is particularly interesting; it includes (among other words), "babe, cupcake, hussy, lady, madam, mama, she-stuff, shrew, temptress, and weaker sex [emphasis mine]."
First of all, "she-stuff"? WTF? She-stuff is like what Buffalo Bill would have called his victims in Silence of the Lambs.
Second, isn't it sad that we lost a word like virago when there are so few words that are defined as "a woman of strength and spirit"? When I see those two definitions of virago side by side, all I can think of is how often I get the message that strong women are bitches, smart women are unattractive, and opinionated women are just loud.
I'd take the world where virago is an honor rather than an insult, any day.