Long division (3)
(Other definitions for eon that I've seen before include "Long period of time" , "Major division of geological time" , "Very long period (US and technical spelling)" , "billion years" , "Vast period" .)
(Other definitions for aisle that I've seen before include "Part of a church" , "A key" , "Part of supermarket" , "The way to get married in church?" , "Way between seat blocks" .)