As used in this chapter, the terms "bank", "bank holding company", "subsidiary", and "Board" have the meaning ascribed to such terms in section 1841 of this title. For purposes of this chapter only, the term "company", as used in section 1841 of this title, means any person, estate, trust, partnership, corporation, association, or similar organization, but does not include any corporation the majority of the shares of which are owned by the United States or by any State. The term "trust service" means any service customarily performed by a bank trust department. For purposes of this chapter, a financial subsidiary of a national bank engaging in activities pursuant to section 24a(a) of this title shall be deemed to be a subsidiary of a bank holding company, and not a subsidiary of a bank.