In this score for harp, there's this weird symbol: (outlined in red)
I have no idea what it means, is it some kind of glissando?
The overlaid circle and plus generally mean damping a string. Combining that with small noteheads and a range shows which strings to damp. Harmonically this makes sense here, to prevent those low strings, plucked in the previous bar and a half, from polluting the C major chord that follows.
Here's another example of exactly that symbol, along with variations.
Whilst it looks rather like a Coda sign, I think it means damp the strings. But exactly how, and when I couldn't find. It's not any kind of gliss.