the president of the United States.
(lowercase) the governor of a U.S. state.
(lowercase) the head of a government.
Origin of Chief Executive
An Americanism dating back to 1825–35
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for chief executive
the person with overall responsibility for the efficient running of a company, organization, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012