Tank

Noun: Tank
Sometimes also humorously referred to as "meatshield," Tank is a term that denotes a warrior. Warriors are called tanks because they have the highest armor level in the game and as such have the highest resistence to damage. The antonym of a tank is a "squishy". Tanks can be one of two types:

Offensive Tank
A warrior specialized in heavy damage dealing. His/her primary focus is engaging the biggest threat in the enemy and quickly rendering it lifeless. His tools include knockdowns, bleeding and deep wounds. An Offensive Tank's biggest fear is hexes like Empathy that cause an attacker to lose health as well as negative conditions like Blindness that cause an attacker to miss.

Defensive Tank
A warrior fortified with all possible defensive tactics to soak up as much damage. A Defensive Tank will charge the enemy but will focus mostly on engaging the frontline of the enemy and keeping them busy fighting him/her. Defensive Tanks will use shields, stances and -if applicable- Protection Prayers to minimize damage inflicted upon them. They can take quite a long while to kill. Defensive Tanks can be used as booby traps using AoE spells that are centered on the caster such as Symbol of Wrath, or Balthazar's Aura.

To tank
Standing still and taking a beating from enemies instead of running away or kiting. Tanking is often used in PvE to make the healer's life easier (only one person to concentrate on). Tanking is especially effective in combination with Protection spells and stances.

It's important to be conscious of certain expectations while tanking:
 * Tank-on-Tank: This means that when assaulting an enemy group, the tanks should attract the aggro of the enemy tanks and keep it focused on themselves. Warriors who rush past the enemy warriors and head for the enemy spellcasters make bad tanks because they allow the enemy warriors to get to their spellcasters.
 * No running back: While tanking, warriors should not, when the going gets rough, run back with their tails between their legs. Instead, warriors should trust their monks and if concerned, they should run sideways and/or dodge. Pulling enemies into the heart of your spellcasters is a sure fire way to kill a few of them as well as get your monks in a panic which means they will not focus on healing you.
 * Keep tanks alive at all costs: A tank that has suffered multiple deaths and is running aroud with, say, 35% DP is of little use to the party in terms of tanking. The reduction to health greatly limits their ability to take damage. As a monk, if you have to choose between healing the tank and healing an elementalist, keep the tank alive. The elementalist can operate with 35% DP from the back if the tank is doing his job, the inverse is not true. A warrior who does not tank and instead rushes off to kill enemy spellcasters forfeits that privilege.
 * Prevention is better than treatment: With the exception of facing powerful mesmers who Shatter Enchantments, a group is best served by using Protection Prayers on their tanks (along with healing) than by just trying to spam healing on them. Protection allows the monks to control the amount of damage inflicted on tanks and thus protects from the unexpected hit that suddenly kills a tank.