You could have achieved the same thing by typing "define aglet" -- or just "def aglet", or even "def this". (Ubiquity understands "this" to refer to the selection.)
Defining words is oft-taken action. Ubiquity makes it easy. Try, for instance selecting the following word: "aglet". Now issue "define". Notice that Ubiquity defines the selection. You could also issue "def this" and Ubiquity will know what you mean.