Overcultivate refers to the process of excessively tilling or managing agricultural land, which can lead to soil exhaustion and decreased crop yields. As such, some synonyms for this term could include overfarming, overworking, overusing, or overexploiting. These phrases imply an excessive level of activity or usage which can negatively impact the quality or productivity of a given resource. Alternately, one could use the phrase to describe someone who is placing too much attention or excessive pressure on a particular area, such as an overburdened manager or an overstressed athlete. Overall, these synonyms suggest an unsustainable level of activity that can have detrimental effects if left unchecked.