A counter-troll is someone versed in the art of disarming an online troll
, usually by out-witting, out-exasperating, or purposefully failing to be antagonized by the troll's actions.
These actions are different from feeding the troll
as the latter involves giving the troll ammunition and sating its hunger for chaos and bedlam, whereas counter-trolling involves responding to the troll in a manner that leaves him/her with nowhere to go in terms of antagonistic actions, and will likely deter him/her from further trolling
Note: Counter-Trolling must be done very carefully, as a desperate troll won't understand what's going on and resort to general pandemonium, resulting in combustion, turning the troll into a flamer