A crew-served weapon is, as the name implies, any weapon system which requires more than one individual to operate effectively. A crew-served weapon may simply be too large for one person to carry, might require specialized training to load, aim, or fire, or require specialized support equipment to function or maintain. One purpose of dieseltech auto-armor is to enable an operator to carry oversized weaponry, including crew-served weapons, though ground and air vehicles can also fill this role.
In the Manifold, crew-served weapons are distinguished from many other weapon types by the fact that they do not come in variants which could normally be carried by a single individual humanoid. For example, while there are both personal and auto-armor variants of the Grease Gun or GF-1 "Tarantula" Assault Needler, the MH-2 "Monarch" Mellification Cannon or BX-9 "Smokestack" Automatic Scattergun have no such personal variant.