Dictionary use can improve reading comprehension and incidental vocabulary learning. Nevertheless, great extraneous cognitive load imposed by the search process may reduce or even prevent the improvement. With the help of technology, dictionary users can now instantly access the meaning list of a searched word using a mouse click. However, they must spend great cognitive effort identifying the most appropriate meaning for a given context, contributing to the disruption of the flow of reading and decreasing the positive effect of dictionary use. Furthermore, dictionary users face difficulty in exploiting accumulative illustrations from multiple contexts to understand obscure words whose appropriate meanings are not in the dictionary or are difficult to identify. To address these issues and to offer language learners, especially lifelong learners, effective support for incremental and incidental learning of vocabulary through reading, this research proposes a dictionary interface named "RoLo" ("RemindonLookup"). Each time an unfamiliar word is re-looked up, RoLo reminds users about contextual information and word knowledge learned in previous encounters of the word in an appropriate manner. Two studies were conducted to evaluate RoLo. The first study, with 34 participants, examined the effect of RoLo use on incidental vocabulary learning. The second examination, involving 43 participants who used the prototype of RoLo for one month, investigated dictionary users' evaluation of RoLo. The results show that RoLo helps dictionary users enhance vocabulary learning and text comprehension and search for unfamiliar words more easily and faster. (Contains 5 tables and 5 figures.)