How to interpret "as of" in "violent or brutal acts as of thugs"

violent or brutal acts as of thugs is an abbreviated sentence. All dictionaries use the same or similar system to save space.

The full version would be:

Thuggery. This word refers to violent or brutal acts that are performed in the manner of thugs. (Or in the manner in which thugs perform them.)

You will see that "as" is an adverb, and of is a preposition.

violent or brutal acts as of thugs

This is a much abbreviated expression. There are various ways to expand it. My suggestion is:

violent or brutal acts [such] as [those that are characteristic] of thugs