weed-eater

informal A tool that uses a motor to spin a thin, flexible plastic cable at the end of a long handle in order to cut grass or other plants in hard-to-reach locations or at irregular angles. Technically known as a "string trimmer," but more commonly known as a "weed-whacker"; sometimes hyphenated. You really need to start using the weed eater to cut the grass along the fence that the mower can't reach.