Characterized by movement of the lips or other speech organs without making audible sounds: subvocal speech. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "subvocal" in a sentence
"So once again, too, with such a textual effect in subvocal mind, a compelling line of descent sketches itself between Romantic visionary enterprise and"
"Literary evidence on this point concerns the way voice returns from its requisite linguistic suppression by wording only in subvocal reading."
"The subvocal note/dɔɡz/is not bound to a singular icon but rather evokes a montage of many — bull-dog, doberman, rottweiller — overlaid like the images of an experimental film."