Q:

Naming convention to warn that branch is likely to be rebased

I sometimes push branches to a publicly-accessible repository (e.g. github) knowing that they contain half-baked commits, works in progress, and other sorts of things that are very likely to be rebased. 
Is there a generally-understood naming convention that would serve to warn those cloning my repo that this branch is not a good one to build their work upon? 
I know I can put warnings in the commits on these branches, but I'm looking for a convention for the branches themselves. 

A:

Is there a generally-understood naming convention that would serve to warn those cloning my repo that this branch is not a good one to build their work upon? 

No, nothing official. 
The only norm is that master is supposed to be ready to run. 
Since you can use / in the name of a branch, jthill's comment is as good an option as any: a WIP/xxx namespace.