This means when a whole bunch of musicians get together play some chords for about a minute saying random lyrics and then go on playing for 19 more minutes.
When a group of bros take turns having sex with a jar or squeeze bottle of jam or jelly (preferably squeeze bottle). Can substitute marmalade as well. No preserves for fear of chunks in urethra.
I got together with my old college roomates this weekend and we had a solid 2 hour jam session.
A door wall is a sliding-glass door or patio door. The term is yet another example of banal Michigan vernacular, where in the residents latch on to company names, trademark names, marketing terms and product names from local companies. The terms become embedded in the local vocabulary and eventually become accepted as actual valid words and phrases. In this case the term comes from Wallside Windows in Taylor, MI (a large window manufacturer), where 'door wall' is their created word for sliding-glass door.
"Bob! John's gonna bring over them doorwalls from Wallsides on Tuesdee afternoon 'round two-thirty. Get 'er done!"