1.  loader(n = noun.person) dock worker, dock-walloper, docker, dockhand, dockworker, longshoreman, lumper, stevedore - a laborer who loads and unloads vessels in a port;
is a kind of jack, laborer, labourer, manual laborer
Derived forms verb load₁, verb load₄

2.  loader(n = noun.person) - an attendant who loads guns for someone shooting game;
is a kind of attendant, attender, tender
Derived form verb load₂

   One who, or that which, loads; a mechanical contrivance for loading, as a gun. [1913 Webster]

loader, n.
1 a loading-machine.
2 (in comb.) a gun, machine, lorry, etc., loaded in a specified way (breech-loader).
3 an attendant who loads guns at a shoot.

Derivative:
-loading adj. (in comb.) (in sense 2).

muzzle loader