The term 'Biblical Verb Form' refers to the verb forms used in the Bible, which are often different from those used in modern English. The three words given as solutions to the crossword are all examples of Biblical verb forms: 'Hast' is the second person singular form of the verb 'HAVE, ' 'Dost' is the second person singular form of the verb 'DO, ' and 'Saith' is the third person singular form of the verb 'SAY.'