Version 4.8.4 introduces the ability to search for user meta data, i.e. data in the (wp_)usermeta table.
This table contains a variety of data, e.g. the user’s first and last name, user roles, and many others, added by WordPress core or by plugins.
Out of the box, BP Profile Search supports only a handful of user meta data: first_name, last_name, role, total_friend_count, total_group_count.
To add your favorite user meta data to that basic initial list, see User Meta Data.