Yes. The definition of "governing body" includes any group of persons who are getting together under authority delegated by a governing body.
But I can talk to one other member of a governing body without it being a meeting, can't I?
Yes, as long as the two of you are not a quorum of a three-member governing body (including committees) and the discussion is not part of a sequence of individual conversations, which collectively involve a quorum of a governing body. But be aware that if members of a governing body participate in a series of individual conversations that collectively constitute a quorum of the governing body, those conversations are a meeting.
If we hold an open meeting, do we have to allow the public to address the governing body?
No. The right to attend an open meeting does not include the right to participate in that meeting. However, other statutes may require a public hearing at which the public is allowed to comment on specific subjects.