From the wonderful RedGuides Wiki

This command is added by EverQuest

Syntax Key
Notation Description
Text without brackets or braces Required items
<Text inside angle brackets> Placeholder for which you must supply a value
[Text inside square brackets] Optional items
Vertical bar (|) Separator for mutually exclusive items; choose one
{Text | inside | braces} Set of required items; choose one
Ellipsis () Items that can be repeated
Syntax /guildsay <text>
Description Sends <text> to guild chat. Seen by all in your guild. Common abbreviation: /gu



The command /gu Hello friends!
will result in the following:
You say to your guild, 'Hello friends!'

See also