1. Literally, to bury something under the surface of the ground by turning the soil up over it. In this usage, a noun or pronoun can be used between "plow" and "under." The once lush forests of the area were eventually plowed under to make room for fields of corn and wheat. We had to plow the entire field under because the market prices for corn had fallen so low.

2. To cause someone to be extremely busy; to overwhelm someone. In this usage, a noun or pronoun can be used between "plow" and "under"; usually used in passive constructions. Kate's not coming tonight because she's plowed under with research for her thesis. The boss has plowed me under with way too many projects—I'll need some help or I'll never finish them on time!