or use 'grep':

    $ man grep | grep recursive
                  directory,  recursively,  following  symbolic links only if they
                  Exclude  directories  matching  the  pattern  DIR from recursive
           -r, --recursive
                  Read all files  under  each  directory,  recursively,  following
           -R, --dereference-recursive
                  Read all files under each directory,  recursively.   Follow  all