Someone else will likely weigh in, but... The drop, in a suit, refers to the waist of the companion trousers, (42 with a standard drop of 6 would have 36-waist pants). Of course, a steeper drop (7 and 8s are common in Italian designers) would require some slimming of the jacket as well. These drops are sometimes referred to as "athletic" cuts. Sportcoats, particularly from higher end makers, have a drop listed that indicates the relative slimness of the waist of the jacket. A 42 jacket with a drop of 8 will be slimmer throuhg the waist than a 42 with a drop of 6.