According to Merriam-Webster: in large quantities.
According to CSGV: Two.
As stated in the new ATF Form 3310.12:
This form is to be used by licensees to report all transactions in which an unlicensed person acquired, at one time or during five consecutive business days, two or more semi-automatic rifles larger than .22 caliber (including .223/5.56 caliber) with the ability to accept a detachable magazine.
Must be the results of being educated under that ole New Math 😉