Probably they mean posters or oral presentations accepted at conferences. Poster abstracts from some of the larger society/association meetings are published in supplemental issues of their respective journals. For example, Journal of Clinical Oncology publishes abstracts of accepted presentations at the ASCO annual conference. But I'm not sure they necessarily mean abstracts that were published in a print journal. More likely they are simply referring to a lack of research products on your CV (posters being usually easiest to get accepted).
