Unlike hybridization or cross breeding, according to "GMO Education", genetic engineering takes DNA out of a species and forces it into another unrelated species.
The same article also states that the plants could also have a decreased nutritional value by inserting a gene that may decrease the mineral nutrition value.
It also says that "the FDA has rejected labeling under the argument that GE foods are “substantially equivalent” to their non-genetically engineered counterparts".
"More than 60 countries already label genetically engineered (GE) foods, including all of Europe, Australia, Japan, China and Russia. The U.S and Canada still refuses to label" ("Ways the FDA Has Failed Consumers").
The best way to keep from eating genetically modified foods is to read the label. If the bar code is five digits and starts with an eight, it is genetically modified.