Our word of the week is
vigliacco, "coward." The common adjective is
vile ("cowardly,"
not "vile"- it's a false friend)(although cowards are vile). The abstract noun is
vilta' ("cowardice") and a single act of cowardice is a
vigliaccata.
A synonym, somewhat less common, is codardo. The abstract noun is codardia.
If you want to insult someone, vigliacco is better, as it has that nice, hard -acc sound that sounds like a reproof in itself.
