No; the medial frontal gyrus is medial; it faces the sagittal midline of the brain. Medial is the opposite of lateral; the dorsolateral prefrontal cortex is lateral, facing towards the outside of the brain.
Perhaps you are thinking of the middle frontal gyrus?
I think the definition you found from OED is fine. Dictionary definitions are often not really ideal for terms used in biology, you learn more from examples and usage, for example the quote you gave about upper motor neurons.
can I say that a neuron projects to another neuron, to mean that the axon of the first connects to some dendrite of the second?