one who spends copious amounts of time and energy to ensure no stone is left unturned (literally) in their pursuit of a goal when all sanity dictates abandoning the cause
he's such a grass cutter, spent 4 hours looking for a matching sock rather than get another pair
A large rodent (rat) caught and raised for market sale in some African countries, mainly in the Northwestern ones {Ghana, Ivory Coast, Benin etc.), used to prepare a variety of dishes.
Lonely Planet backpacker Megan McCormick ate a grass-cutter in her stay in Ghana.