On-line Documentation
MAN -K KEYWORD prints one-line summaries of all commands whose table of content entries contain any of the keywords.
host% man -k password
passwd (1)- change login password
passwd (5)- password file
vipw (8)- edit the password file
getpass (3)- read a password
yppasswd (1)- change login password in yellow pages
host man 5 passwd