Search the whatis database for strings.
apropos <keyword>
$ apropos partition
testdisk(8) - Scan and repair disk partitions
fdisk(8) - DOS partition maintenance program
gpt(8) - GUID partition table maintenance utility
pdisk(8) - Apple partition table editor
fdisk(8) - DOS partition maintenance program
gpt(8) - GUID partition table maintenance utility
pdisk(8) - Apple partition table editor