Sentence:  ... the chairman of the gathered scholars ... [shushed] the black waiters preparing to feed us a hefty lunch behind the <WSD>bellowsed</WSD> dividing wall with the impatient yell, “You're disturbing our meeting,” while we discussed their plight on our side of the wall. 
Meaning of the word marked with <WSD> tags:  To fold up like a bellows; to accordion.