Can't remember it. Tried to google it with no luck. I encountered it last week but the browsing history is wiped.
Here's what that command does. You just write it in terminal with some word. It will search through all the manuals from repository and print out the list of matches with short description.
man <command> | grep -A 10 '<escaped_option>'
, where<escaped_option>
is e.g.\-a
– kos Jun 10 '15 at 19:32