Paid resource
新华字典 (Xinhua Dictionary)
My notes
Only relevant once you're deep enough into the language to think and define in Chinese — which won't be most people reading this. I mention it because at higher levels a monolingual dictionary forces a different kind of engagement with the language, but don't rush to it.
I started using the Xinhua Dictionary when I noticed that defining words in English was creating a translation layer that slowed my thinking in Chinese. Forcing myself to read a Chinese definition and understand it in Chinese — without mapping it to English first — was uncomfortable at first but accelerated the shift toward thinking in the language rather than through it. This is genuinely only relevant once you're at a level where you can already understand most of the definition text; I would not recommend it before you're comfortably reading HSK5-level material.