From Diablo Wiki
A Meat Shield is a generalized term, often referred to in MMOs and other genre of RPGs as tanks. A meat shield is a player or NPC who can absorb large amounts of damage, effectively "shielding" more fragile characters from harm's way while they deal damage. The damage-dealing character is referred to, in a general sense, as dps, or Damage Per Second.
There's a three-pronged class dichotomy that exists in many style of games, sometimes referred to as a trinity, which defers standardized class roles to different players. The three functions of this dichotomy are: Tanks, DPSers, and Healers. Diablo traditionally hasn't had a healer role outside of some varied, rare Paladin builds in Diablo II, but the tank role can often be filled by various classes. However, with a lack of a proper aggro or threat system, the prominent role of a tank in an ARPG is somewhat diminished.
Visit to the tank reference page for further information.
More reference terms.