Referring to 100 round drum magazines, also known as drum mags or beta mags. Most reffering to double drums on one magazine hanging below the firearm like a scrotum.
A chafe recieved between the upper thighs and asscrack brought about by sweaty activities such as walking back and forth or working out of doors. Produces a Baboon-likerash on the buttocks.
"Man, I got a serious case of monkeybutt bartending tonight!" or "Landscaping gave the rudest monkeybutt yesterday!"