"prefacing" in the verb sense
1. precede, preface, premise, introduce
furnish with a preface or introduction
"She always precedes her lectures with a joke"
"He prefaced his lecture with a critical remark about the institution"
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License