Reference security means a security into which a security that is the subject of a distribution (subject security) may be converted, exchanged, or exercised or which, under the terms of the subject security, may in whole or in significant part determine the value of the subject security.
17 CFR § 242.100
Preliminary note: Any transaction or series of transactions, whether or not effected pursuant to the provisions of Regulation M ( 242.100-242.105 of this chapter), remain subject to the antifraud and antimanipulation provisions of the securities laws, including, without limitation, Section 17(a) of the Securities Act of 1933 [15 U.S.C. 77q(a)] and Sections 9, 10(b), and 15(c) of the Securities Exchange Act of 1934 [15 U.S.C. 78i, 78j(b), and 78o(c)].