the GNU version of the Collaborative International Dictionary of English
ad. In a presumable manner; by, or according to, presumption.
The Century Dictionary and Cyclopedia
As may be presumed or reasonably supposed; by or according to presumption; by legitimate inference from facts or circumstances.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
ad. by reasonable assumption
Word Usage
"Anyone with the faintest interest in philology will have spotted that ‘gryphon’, from which his surname presumably derives, is a Greek word for a mythical dragon which featured prominently in Persian folkore."