Which plant is described as grasslike and characterized by round stems?

The plant characterized as grasslike with round stems is a rush. This distinctive feature of having round, solid stems sets rushes apart from other similar plants, such as sedges, which have triangular stems, and bulrushes, which can sometimes have round stems but are more commonly associated with broader, leafier growth. Water lilies, on the other hand, do not exhibit grasslike attributes and are known for their broad floating leaves. Therefore, rushes are the correct identification when looking for a plant that has a grasslike appearance and round stems, fitting the description in the question perfectly.