The geometric form of the cross-section of a groove. It is defined in terms of the radius of the bottom of the groove (bottom radius) and the included angle between the walls of the groove (groove angle).
"A few years ago, my mother gave me some reel-to-reel tapes that her and my father exchanged back in 1967 while he was serving in Viet Nam as an officer in the Marine Corps. He died in 1972 when I was 8 years old. Neither my mother or I have a RtoR player so we weren't sure if the 30+ year old tapes were salvagable. I sent them into you and I ..."