It is not possible to edit the definitions or glosses from the interface.
There are versions for some additional languages like Spanish, Portuguese, French, Indonesian. You will see these versions by choosing one of these languages for the whole Paratext interface from the "Main Menu - Paratext Settings".
If you added a biblical term you can edit the gloss from the Biblical Terms - (Colum Edit) Edit Term menu. You can include there both the gloss and the definition that is useful to you.
Another way in case you need to edit a specific term that is causing confusion could be achieved by editing the file in \My Paratext 9 Projects\NameProject\ProjectsBiblicalTerms.xml where the Gloss tag could be modified, but it should be done very carefully with the help of someone who knows how to handle this kind of files, otherwise it could damage it (maybe someone else could confirm if this has any additional risks).
The management of the Bibical Terms list has its details, you can read this post: https://support.bible/8504/how-to-edit-biblical-term-added-from-all-biblical-terms-list