By analogy with sunblock and sunscreen (assuming sunblock deflects the sun's rays and sunscreen absorbs them), a cockscreen does not block cock, she absorbs it. Thus, you are not completely blocked from the friend, but may have to sleep with the cockscreen first to get through.
"That girl Dana there is being a total cockblock for her hot friend Jennifer!"
"Nah, she's just a cockscreen. Give her some lovin' and you'll get through, trust me."
Hickish or redneck-related; backwater. It can also refer in a more general sense to an item or custom that has lagged hilariously behind its contemporaries or is just garishly out of place. Derived from onomatopeoia of the beginning phrases of a banjo lick, as in the infamous "Dueling Banjos" from the film Deliverance. Optimally pronounced with a bit of a twang, closely assonating the puckish thwap of a banjo string.
I usually like camping, but all these bern dernts with their generators are keeping me awake.
See that guy over there with the mullet and the Marlboro t-shirt--yeah, bern dernt. Let's get out of here.