president vs presiding officer

president and presiding officer both are nouns.

Word	Noun	Adjective	Verb	Adverb
president	Yes	No	No	No
presiding officer	Yes	No	No	No

As nouns, presiding officer is a hypernym of president; that is, presiding officer is a word with a broader meaning than president:

president (noun)	presiding officer (noun)
the chief executive of a republic	the leader of a group meeting
an executive officer of a firm or corporation
the head administrative officer of a college or university
the officer who presides at the meetings of an organization