June 1, 2016
Literally translated, this means white wedding (or white marriage). But it does not at all mean the same thing as that phrase in English.
When we talk about a white wedding, we are talking about a formal wedding in which the bride wears a white dress, with a traditional ceremony, followed by a reception.
In Italian, a white wedding is an unconsummated marriage.
In many cultures, the color white symbolizes purity. In the past, many people considered a bride's white wedding dress a symbol of her virginity, and the phrase "white wedding" was sometimes used to imply (or boast) that the bride was a virgin. Today the white gown remains a tradition. In theory, it is worn by a first-time bride, but in reality, many women marrying for the second (or third) time choose white gowns simply because they prefer the traditional look.
It's not clear to me if white (bianco) in the Italian matrimonio di bianco refers to virginity, or if it refers to coldness, the presumed frigidity between the partners. For comparison, another Italian phrase, settimana bianca (white week), means a ski trip, with white clearly referring to snow, but there are also a number of Italian idioms in which white has other meanings.
In any case, if you want to share your excitement about your upcoming white wedding with your Italian friends, make sure there is no misunderstanding. The Italian phrase for getting married in a white dress is sposarsi in bianco.