What is it called when you shout out loudly?

It is called hollering.

Sense 2:

shout, shout out, cry, call, yell, scream, holler, hollo, squall

utter, emit, let out, let loose

Sense 3:

exclaim, cry, cry out, outcry, call out, shout

express, verbalize, verbalise, utter, give tongue to

Sense 1:

shout

talk, speak, utter, mouth, verbalize, verbalise

Sense 4:

abuse, clapperclaw, blackguard, shout

attack, round, assail, lash out, snipe, assault