It would be wonderful if the top result were displayed in the results/definition pane while typing the look-up query. The list of words already sorts as the query is typed, so it would be just a matter of having the top word display. (As it is, you have to hit enter or the down arrow to get a definition to come up)
As small a feature as this may be, it would make a huge difference for a heavy user like myself. Often I would only have to type part of the word, and then could keep the cursor in the 'Look up' box, ready to type the next query. You've probably already heard this one, but here's one more plea for it. (And thanks for the great work!)