I tried but didn’t find a way.
Usually, for glossaries the best way is to use the List Contents and List Heading styles but this way the “definition” gets in a different paragraph than the “term”. You want something more similar to a dictionary instead.
Under HTML I would try making a paragraph float, but this would be unpredictable. Besides LibreOffice doesn’t have such functionality anyway; you would need to create a frame for each “term” manually, so this is a no-go.
I tried using “Drop caps” for whole words which lets you apply an arbitrary style, but the interface forces you to use 2 or more lines. If it let you do a 1-line drop cap, you could get the desired effect, except that for words with non-breaking hyphens only the first side of the word gets dropped.
Still, even though this can’t be done automatically I recommend creating a Character Style named “Inline term” or the like, setting it to Bold and using it to manually mark your terms, so you can clear your Direct Formattings using Ctrl+M to the whole document without hurting the bold for your terms.