"He would be out of his depth in a parking lot puddle."
"A gross ignoramus - 144 times worse than an ordinary ignoramus."
"When his IQ reaches 50, he should sell."
"A photographic memory but with the lens cover glued on."
"A prime candidate for natural deselection."
"Donated his brain to science before he was done using it."
"If you give him a penny for his thoughts, you'd get change."
"It's hard to believe that he beat 1,000,000 other sperms to the egg."
"One neuron short of a synapse."
"Some drink from the fountain of knowledge;..... he only gargled."
... still means stupid.