I think the real question is "what do you call a single figure or column of figures under a bass note". So far as I am aware, the term "figured bass" means a bass line (not a single note) that has figuring to indicate the harmonies.
If I want to talk about a number of such bass lines - e.g. the bass lines of several pieces so notated - then I would call them "figured basses".
I'm not sure that I have ever heard of a term to describe one single harmony so notated.
Not a very helpful answer to your query, perhaps, but that's the usage I am familiar with.
David
On Tue, 2021-06-15 at 16:20 +0200, Jacques Menu wrote:
Hello folks,
What would be the plural of ‘figured bass’, if that applies, to denote several occurrences of the figures in a score, the same way has there can be several harmonies? Maybe ‘figured bass figures’?
In the example below, there 5 such occurrences:
Thanks for. your help!
JM