Wordnet 3.0
NOUN (1)
1.
an Italian title of respect for a man;
equivalent to the English `sir';
used separately (not prefixed to his name);
The Collaborative International Dictionary of English v.0.48:
Signor \Si*gnor"\, Signore \Si*gno"re\, n. [It. See Seignior.]
Sir; Mr.; -- a title of address or respect among the
Italians. Before a noun the form is Signor.
[1913 Webster]
WordNet (r) 3.0 (2006):
signore
n 1: an Italian title of respect for a man; equivalent to the
English `sir'; used separately (not prefixed to his name)