While trying to mount a filesystem, the mount(1M) command received a "Device busy" (EBUSY) error code. There are several possible reasons: this /dev/dsk filesystem is already mounted on a different directory, the busy path name is the working directory of an active process, or the system has exceeded its maximum number of mount points (unlikely).
Run /etc/mount to see if the filesystem is already mounted. If not, check to see if any shells are active in the busy directory (did the user cd(1) into the directory?), or if any processes in the ps(1) listing are active in that directory. If the reason for the error message isn't obvious, try using a different directory for the mount point.