What does "glacier collapse" mean?
The word collapse is not appropriate in the case of a hanging glacier such as the one you mention in your question. A hanging glacier is a glacier that terminates at a cliff edge. Since glacier ice is constantly moving towards the cliff, the terminus will occasionally lose sufficient support and detach from the glacier causing an ice avalanche. As long as the glacier feeds ice to the cliff edge ice avalanches will continue to occur. How often will largely depend on the ice velocity moving ice towards the cliff edge. This is thus a natural behaviour and not a collapse, or at least not named collapse in glaciology.
The word collapse is not a scientific term and does not have a unique definition in glaciology. In the case of an ice shelf that suddenly breaks apart such as the Larsen B (Rott et al. 1996) the term collapse has been used in articles. In this case the event was sudden and the entire ice shelf broke up and was lost during a few months. At the same time collapse is commonly used to describe other phenomena such as the loss of an ice sheet or part of an ice sheet (for example, Brendryen et al., 2020). Such a process is much slower than the ice shelf collapse, perhaps lasting many hundreds or thousands of years. But the word is used because it describes an irreversible event or development.
So coming back to the hanging glacier, its avalanches is an ongoing process and the word collapse gives the wrong impression. The glacier is not collapsing. Given climate warming the glacier will likely decrease in size and the avalanching change, possibly stop depending on the bedrock morphology on which the glacier sits. If the climate warming causes the glacier to completely melt away, then that could be considered a collapse of that glacier. But when you read different scientific articles on glaciers you will see the word used in many different ways so a tricky word to use in a good and consistent way.
References
Helmut Rott, Pedro Skvarca, Thomas Nagler, 1996 Rapid Collapse of Northern Larsen Ice Shelf, Antarctica. Science, 271 (5250) 788-792
Brendryen, J., Haflidason, H., Yokoyama, Y. et al. 2020 Eurasian Ice Sheet collapse was a major source of Meltwater Pulse 1A 14,600 years ago. Nat. Geosci. 13, 363–368.