Doug is right. There is a distinction to listen for when listening on the radio.
Ordinary whole grain corn meal = poor fertilizer (relatively) but a great tool to combat lawn disease
Horticultural grade corn meal = not the stuff you buy at the grocery store but the stuff you get at a feed store. Or in Howard's description it is probably only available at your local garden nursery. I don't know about that. I get the plain brown bag at the feed store for anywhere from $3 per bag to $15 per bag depending on the market price of corn.
Corn GLUTEN meal = excellent fertilizer and might also have some preemergent qualities. From what I read on the other lawn forums, nobody is really having success with CGM as a preemergent. I used it last year at a rate of 20 pounds per 1,000 square feet per month for 8 months in a row and never saw any decrease in weed pressure. I don't have many weeds but I have a few. I was primarily using CGM as a fertilizer to really boost my lawn. It worked!!