I think Astonish has said it all.A CIDian is a die-hard fan of CID and the characters. People who are used to seeing them every weekend 10PM at their homes to an extent that the main actors and characters are like family. Just as one doesn't desert one's family members/relatives/friends when they fall into bad times, a CIDian doesn't desert the CID team on screen.
A CIDian is one who learns from CID. Be it lessons on beng alert, watchful and observant, dealing with losses in life or dealing with conflict between duty and personal life, lessons on friendship, lessons on how to(and how not to) behave at workplace - a CIDian can derive lessons on all these things from CID. These things are not visible to casual watchers of the show. Only a true CIDian can notice these.
A CIDian is one who watches an old CID episode to relax.
A CIDian is one who never tires of admiring the trio.
A CIDian is one who forgives the crew and writers for all the nonsensical episodes.
A CIDian is one who knows the characters better than the actors themselves.
A CIDian is one who has a secret wish to meet them all some day. đ