Most people believe Summa Cum Laude is an honor ... Publix grocery store believes it's obscene.

Case in point ... this cake.

A woman in South Carolina ordered the tasty treat online to celebrate her son graduating from his homeschool program with a 4.79 GPA ... earning Summa Cum Laude honors.

But, when she sent a friend to pick up the cake, the word "Cum" was edited out -- an apparent violation of the grocery store's obscenity policy!!!!

"My son was humiliated," the woman posted on her Facebook page ... "I seriously couldn't make this crap up!!!"

"How utterly ridiculous and I will be speaking to a manager for a refund. Shame on you Publix for turning an innocent Latin phrase into a total embarrassment for having to explain to my son and others (including my 70 year old mother) about this joke of a cake."

FYI, "Summa Cum Laude" is a Latin phrase that means "with highest honor."