The official GemStone IV encyclopedia.
MUTTER is a roleplaying verb. It can be used to mutter a single word as well. It can also be used with the preposition "about" and a single word.
You mutter something inaudible. Person mutters under her breath.
You mutter something. Person mutters something.
Mutter about something:
You mutter something about something. Person mutters something about something.