I tend to see the derogatory ‘Liberal’ and moreso ‘Lib’ used for Neo-liberals and those supporting the neoliberal policies that have dominated the last few generations.

I otherwise see it used in the context of the phrase “scratch a liberal and a fascist bleeds” which is pithy but tracks with history and typically the more antagonistic usage. It is almost entirely used to provoke a reaction from the ‘libs’ it is directed at, accuracy notwithstanding.

With context it is almost always pretty self explanatory which is being used.