The dictionary stinks. :(
Almost every word I've tried to put in there it won't translate. And I noticed that even with other languages, it won't play how the word sounds for you--which, especially in Gaelic, is a MAJOR let down. You really ought to be able to hear how it's pronounced.
This course has a Words list (different from the dictionary) for the words in the course. From the learn page find the "... More" button at the top of the page. The 3rd item in the list is "Words". Open the list. Click any word. You will see the translation and a sound icon. There will also be several sentences that use the word along with sound icons for those sentences.
For other Scottish Gaelic words go to LearnGaelic.scot. There is a dictionary and nearly every word or phrase listed has sound to go along with it.
EDIT - I'm using the website version of Duolingo, not the app.