What does "spiralling" mean?

[Saluki]

I feel silly asking this question, but when someone tells me they're "spiralling", or saying "when I spiral", what does that mean?
I don't know what it means. Is it having a panic attack, or is it an ef or is it intrusive thoughts one can't control or is it a combination of many things? I hear the term a lot and I can't figure out if I "spiral" because I don't understand what it means.  People use this term a lot so I feel like I need to know what it means! Thank you!