Wiktionary
a. Of a corporation or other business, owned by a small number of people, and not having shares of ownership sold via a stock exchange or other public market.
Usage examples of "closely held".
I've never been asked to show my trick bellybutton before, because up to recently it has been a closely held secret.
They do not recognize our principle of religious freedom, and if we allow something that offends their closely held beliefs, then in their mind it's our fault.
Crypto City's budget, long a closely held secret, has been revealed in a closed-door meeting in the City's Engineering and Technology Building.
Or it might be something more subtle, something that would be noted by an obscure graduate student in some locale remote from Washington, DC, who, if the arguments were closely held and highly secret, would never have the opportunity to address the issue.
The existence of the Skinks--or any alien sentience--was a closely held state secret.
The exact composition of the tags was a closely held secret, supposedly only known by the Tribunes.
I doubted that, but it was closely held enough that there were no records in the Archives or anywhere else that I could find.
Even with her Bene Gesserit powers of observation, she had trouble penetrating Leto's closely held thoughts.
Maison Long to be a closely held corporation, fifty-one per cent to you two, forty-nine percent to me, all three of us directors, and we can't sell stock save to each other-except that I retain option to change all or part of my share to nonvoting stock, in which case I can assign it.