California Code, Civil Code - CIV § 2953.1

(a) “Real property security instrument” shall include any mortgage or trust deed or land contract in or on real property.

(b) “Subordination clause” shall mean a clause in a real property security instrument whereby the holder of the security interest under such instrument agrees that upon the occurrence of conditions or circumstances specified therein his security interest will become subordinate to or he will execute an agreement subordinating his interest to the lien of another real property security instrument which would otherwise be of lower priority than his lien or security interest.

(c) “Subordination agreement” shall mean a separate agreement or instrument whereby the holder of the security interest under a real property security instrument agrees that (1) his existing security interest is subordinate to, or (2) upon the occurrence of conditions or circumstances specified in such separate agreement his security interest will become subordinate to, or (3) he will execute an agreement subordinating his interest to, the lien of another real property security instrument which would otherwise be of lower priority than his lien or security interest.