Person. The term person includes a natural person, partnership, association, other unincorporated body, corporation, or body politic, having or claiming an interest in vested property or liable or charged with liability for internal revenue tax in connection with such property.
26 CFR § 302.1-1
General. When used in the regulations in this part, the terms defined in this section shall have the meaning so assigned to them. A term not defined herein shall have the meaning, if compatible with the context, imputed thereto under the internal revenue laws.