Filaceous is an adjective that describes something that is thread-like or composed of threads. There are several synonyms for filaceous, including fibrous, filamentous, wiry, stringy, slender, and thin. Fibrous is typically used to describe something that is made up of fibers, such as a tough plant material. Filamentous is often used to describe something that is composed of long, thin strands, such as a string of cells or a spider's web. Wiry is used to describe something that is thin and flexible but also strong and resilient. Stringy is an informal synonym for filaceous that is often used to describe something that is thin and elongated. Slender and thin are both synonyms for filaceous that describe something that is narrow in girth.