Cylindrical (keycap shape)
Provided by the ASK Keyboard Dictionary
A keycap is "cylindrical" if its top has a cylinder-shaped indent. IBM used cylindrical keycaps on its IBM Selectric III electric typewriters, IBM Electronic Typewriter series, Wheelwriter, Quietwriter and Actionwriter electronic typewriters, IBM Model F family keyboards, and IBM Model M family keyboards. In the wider, modern keyboard hobby, the "Cherry profile" is an example of a cylindrical-based keycap profile. It's often used to contrast against spherical and simply flat keycaps.