umount
Unmount filesystems. Remove a special device or the remote node 
  (rhost:path) from the filesystem tree at the point node. If either special or 
  node are not provided, the appropriate information is taken from the fstab(5) 
  file.
SYNTAX
      umount [-fv] special | node
      umount -a | -A [-fv] [-h host] [-t type]
Options
     -a	     All the filesystems described in fstab(5) are unmounted.
     -A	     All the currently mounted filesystems except the root are
	     unmounted.
     -f	     The filesystem is forcibly unmounted.  Active special devices
	     continue to work, but all other files return errors if further
	     accesses are attempted.  The root filesystem cannot be forcibly
	     unmounted.
     -h host
	     Only filesystems mounted from the specified host will be
	     unmounted.	 This option is implies the -A option and, unless oth-
	     erwise specified with the -t option, will only unmount NFS
	     filesystems.
     -t type
	     Is used to indicate the actions should only be taken on filesys-
	     tems of the specified type.  More than one type may be specified
	     in a comma separated list.	 The list of filesystem types can be
	     prefixed with ``no'' to specify the filesystem types for which
	     action should not be taken.  For example, the umount command:
		   umount -a -t nfs,hfs
	     umounts all filesystems of the type NFS and HFS.
     -v	     Verbose, additional information is printed out as each filesystem
	     is unmounted.
FILES
     /etc/fstab	 filesystem table
    
"Be nice to people on the way up, because you'll meet them on your way down." - Wilson Mizner
Related commands:
  
  hdiutil - manipulate disk images 
  mount - Mount a file system
  fstab(5) - 
  
  Equivalent BASH command:
  
  umount(8) - detach/unmount a device