All authors can do, is to depict men out of their business - in their passions, loves, laughters, amusements, hatreds, and what not - and describe these as well as they can, taking the business-part for granted, and leaving it as it were for subaudition.
-- William Makepeace Thackeray, The Virginians
Here, much is left to subaudition - what is obscure is explained by the accompanying look or gesture, and what is hinted at in the unfinished sentence, it is understood by the hearer, whose thoughts outrun the tongue of the hurried talker.
-- George Winfred Hervey, The Rhetoric of Conversation, Ed. by S. Jenner
Subaudition comes almost directly from the Latin subauditiō-, meaning "under" and "to hear."