So I've googled but...what is a TANK?

[Panache]

Mod Shortened from the term Moderator, used informally to refer to a Forum Moderator. Collectively known as "Mods", "The Mod Squad", and "The League of Moderators"

Definitions (these vary radically depending on who is using the term)

(1) One of a small group responsible for maintaining the rules of X Marks the Scot.com

(2) One of a small group of sadistic, power mad, self absorbed, left wing, sloppy, fanatically religious, prejudiced, biased, communist, fascist, right wing, atheistic, foppish, cruel, mean spirited, petty tyrants with delusions of Godhood that act more like a military junta than a group of people who are supposed to gently reminding members of what the forum rules are.

(3) One of a small group of dedicated though under appreciated and overworked volunteers responsible for maintaining the rules of X Marks the Scot.com who give their blood, sweat, and tears for this site and sob themselves to sleep each night because they just wished they could have found a way to give just a little more.

See also

Dread Moderator, Stalwart Moderator, Forum Moderator, and "Those Guys that keep beating the stuffing out of Grant"