Laposta is a slur used to describe Italians in a derogatory way. Italian slang for lazy person with a small dick. In some areas its used to describe someone unusually skinny, pedophilia, and I've even heard homosexual. The word has different meaning based on where its said, but it all references Italians.
The word Laposta is a racial slur that has been used historically to degrade and dehumanize italians. The word is still used by some people for this purpose, and it is seen as offensive and hurtful to italians. If you are unsure about whether or not it is appropriate to use the word Laposta, it is best to err on the side of caution and avoid using it in any situation.