A Door-County-gasm is one of the cumgasms a guy has when he's vacationing in Door County and eats some pot-stickers, gets into an outdoor jacuzzi on a moonless but glittering star-lit night and suck your buddie's dick underwater while he jacks you off with one of your knobby fleshlights until you're almost ready to cum, -- then he pulls it off your cock and you blow your load into the fleshlight, suck it out and sno-ball it, and then you swallow it and do it again.
I went to Door County with Matt, and had several Door County-gasms while there!
A knock on the doorgasm is when you're jerking off and someone knocks on the door while you're at the point of orgasm, causing a very awkard situation in which you can't decide whether to answer the door or simply ejaculate.