modunload —
unload a kernel module
The modunload utility unloads a loadable kernel module
  from a running system.
name is name of the module to be unloaded,
    as shown by modstat(8).
Builtin modules will not be unloaded from memory, but they will be
    disabled. They can be re-enabled using
    modload(8).
The modunload utility exits with a status of 0 on
  success and with a nonzero status if an error occurs.
A modunload utility appeared in NetBSD
  5.0. The modunload command was designed to be
  similar in functionality to the corresponding command in SunOS 4.1.3.