The word Utraquism is from a Latin phrase meaning “under both kinds.” The “both kinds” referred to are both elements of the Lord’s Table (communion, Eucharist.) An Utraquist was someone who believed that those receiving communion should partake of both the bread and the cup.
The traditional Roman Catholic position had been that the laity could only receive the bread (wafer) at the Eucharist, and the wine was reserved for the clergy. This practice was maintained for a number of reasons stemming from the fact that Catholics believe in transubstantiation—that is, the bread and wine actually become the body and blood of the Lord. They also teach that the wafer contains both the body and blood of the Lord. Traditional Catholic practice forbade congregants from partaking of the cup for fear they might spill or drip the blood of Christ, and then it would be trampled underfoot, which would be sacrilegious.
In the early fifteenth century, Jan Hus, a Catholic priest in Bohemia, began objecting to some of the abuses of the Catholic Church. One of the reforms that Hus advocated was allowing the laity to take both the bread and the wine at Mass. This position was called Utraquism, and those who advocated for it (following Huss on this point although not necessarily on others) were called Utraquists. An Utraquist could also be called a Calixtin or Calixtine (from the Latin word for “chalice,” which is the cup that held the wine).
While the Utraquists did push this particular reform, they did not go as far as Hus on many other points. Hus was eventually condemned and burned at the stake, but Utraquists were considered to be generally orthodox Christians according to the Council of Basel in 1433.
In that day and age, religion and politics were thoroughly mixed. If the absolute authority of the Roman Catholic Church could be successfully challenged on a theological point, that might also weaken its political authority. If the Church’s hold over the masses was weakened, other political forces that rallied around the disputed theological point might have the opportunity to gain some popularity and control. This meant that Utraquists posed a threat to the Catholic authorities.
George of Poděbrady was an Utraquist who opposed the pro-Catholic ruling party in Bohemia (the Czech Republic today) and captured the capital, Prague, in 1448. The pro-Catholic Hapsburg king Ladislav was a minor at the time, and a compromise was reached to allow George to rule as regent until the king came of age. Ladislav came to power in 1453 but died suddenly in 1457, and George was elected king in 1458. George refused to bend to the pope’s political wishes, and the pope attempted to turn the nobles against him.
These religious/political hostilities continued in Bohemia for the next 150 years, and during that time a separate Utraquist church was formed. Utraquism became the standard in Bohemia. Finally, an Utraquist army was defeated by the armies of the Holy Roman Emperor at the Battle of White Mountain (near Prague) in 1620. After that, Utraquism was outlawed in Bohemia.
Today, Protestants follow Utraquism, and the laity receive both the bread and wine at communion. The Roman Catholic Church now allows for the priest to have some discretion over whether he will allow it. Official Catholic teaching is that the body and blood of the Lord cannot be separated, so anyone who takes the bread actually receives both the body and blood of the Lord.