guild
An association of men belonging to the same class, or engaged in kindred pursuits, formed for mutual aid and protection.
    Webster's Revised Unabridged Dictionary

Guild, The also The Dark Guild
A secret society of obscure origins and intentions. Evidence of The Guild has only recently come to light and further investigation is required. Presence of Guild members has been indicated in several countries. Guild members appear to use a unique language in recorded exchanges; presumably for secrecy.
    The Orange Dictionary (1952 ed.)

Guildish
The language of The Dark Guild (qv). Linguistic studies have recently elicited the basic structure and skeleton vocabulary of this language. While the small corpus of material available has suggested little of The Guild's wider activities, the language itself appears a broadly logical construct and the vocabulary and idioms themselves may reveal more of The Guild's background and internal culture.
    The Orange Dictionary (1959 ed.)