According to this site, a thesaurus is

a taxonomy that also includes associated and related terms..

where a taxonomy is

a set of controlled vocabulary terms, usually hierarchical.

Well, that aptly describes altmc doesn't it? Except, of course, there isn't any hierarchy in altmc.

Update 31052004: Hierarchy in a thesaurus is in reference to their use of BT (Broader Term) and NT (narrower term).

Update 02062004: The lack of hierarchy in altmc makes it a glossary instead of a thesaurus! Duh, any idiot could have told me that just by looking at it, but I was just hopelessly confused with all the terms in IA. For example, the term 'thesaurus' is used differently from the layman's definition (think: Roget's).