the GNU version of the Collaborative International Dictionary of English
ad. On this; hereon.
The Century Dictionary and Cyclopedia
Upon this; following or on account of this.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
ad. immediately after this
Word Usage
"I made haste, hereupon, to nod my head twiceonce in the negative, meaning thereby that I would prefer not taking the other bottle at presentand once in the affirmative, intending thus to imply that I was sober and had positively come to my senses."