tetrabard - a unit of vocabulary : 60,000 words; hence, a tetrabardian vocabulary is one of that size

"Steven Pinker in The Language Instinct compared
the probable 60,000-word vocabulary of a typical
US high-school graduate with the 15,000 words
used in the complete works of Shakespeare, thus
defining the "tetrabard" as a unit of vocabulary. We
suspect that David Ridpath, who reminded us of this,
may be a jaded teacher: "I can think of a few
centibards I have known," he grumbles."
- New Scientist, Feedback, 13 November 2004