Use x11-misc/dmenu as default. Disable to use a different implementation.

Packages describing “dmenu” as local USE flag

Package “dmenu” Flag Description
x11-misc/j4-dmenu-desktop Use x11-misc/dmenu as default. Disable to use a different implementation.
app-admin/pass Add support for x11-misc/dmenu with the 'passmenu' program.

All packages providing a “dmenu” USE flag (1)