Linking words to definitions

I'd like to make words in my Harlowe story connect to definitions - like a pop-up glossary term. Using (link:) or ( click:) macros aren't doing exactly what I want - I'd rather have the definition text pop up, not be revealed just in line with the text of the story. Even better, I'd like the linked word to open a new browser tab (so I can keep my glossary up to date on a separate page, rather than going into each appearance of a word in the Twine story). But I haven't been able to put my finger on the code for making an external link from the story in the Harlowe user guide. I experimented with straight up html code (using a href="etc...) but that didn't work.

Any tips? Thanks in advance!