Encroaching on can be described in a variety of ways depending on the context. It can be replaced with words like invading, trespassing, infiltrating, or impinging. In certain contexts, overstepping, infringing, or exceeding bounds might be more appropriate. In terms of territory or land, some synonyms include intruding, encumbering, or annexing. In a metaphorical sense, encroaching on someone's time can be replaced with words like impeding, infringing on, or encumbering their schedule. Ultimately, the synonym that fits best will depend on the situation and the tone you want to convey.