What does this sign mean?
'Significa' — si-NI-fi-ca. Stress on the second syllable; hard 'c' before 'a'.
Use this whenever you encounter an unfamiliar sign in Italian. Works in shops, on the street, in museums, or in transport hubs. Pointing at the sign as you ask makes the question clear.
'Cosa significa' means what does it mean. 'Significare' is a regular -are verb meaning to mean or to signify. 'Questo cartello' (this sign) — 'cartello' refers to a sign, placard, or notice. For road signs specifically, Italians also use 'segnale' (segnale stradale = road sign).
Cosa vuol dire questo?
What does this mean?
More colloquial; 'volere dire' literally means 'to want to say'.
Che significa?
What does it mean?
Very short informal version; drops 'cosa'.
Può spiegarmi questo segnale?
Can you explain this sign to me?
Formal request for a fuller explanation.
Italian road signs follow the Vienna Convention and are largely the same across Europe. However, some local signs use Italian text for specific local regulations. ZTL (Zona a Traffico Limitato) signs are particularly important for foreign drivers — entering a ZTL without a permit triggers an automatic fine sent to your home address.