A berry drop happens while munching on a females vag. During the munch session you may notice a semi sweet nutty taste in your mouth. This would be a stray dingle berry that has found its way into your munching vicinity. Hence a berry drop.
Guy one:"Man i dont feel so good today"
Guy two:"Whys that"
Guy one: "Well I was about to go iron chef on that vag last night but during my munching session i got berry dropped.