Here is my current definition:
It is to open your heart completely to another...
and another, and another and another
such that 2 hearts are utterly joined to one another
therefore it is those who open their hearts utterly to God's open and poured out (Spirit-ed) heart, who can be called spiritual and are the best people to deal with 'sinners' (cf Gal 6:1) - who are the best people who have had their planks removed to handle the specks in others