The phrase "grassy flavor" refers to the taste or flavor that is similar to grass. It means that something, such as food or drink, has a fresh and slightly earthy taste like the smell or taste of grass. Full definition
If you want a boost, you can go with a neutral - tasting protein powder (I like Sunwarrior Natural), but I like the slightly grassy flavor of hemp seeds with this flavor combination. (thrivinghomeblog.com)
Wheatgrass powder has a mild grassy flavor with a hint of sweetness that works well with juice, smoothies or water. (nuts.com)
Horsetail tea has a neutral taste and mild grassy flavor, so it can be combined with other ingredients for creating a flavorful tea. (detoxdiy.com)